Develop Reference

Android: How can I create a sliding bottom navigation bar like this?

How to create a bottom navigation bar with a snap-able indicator that always centers the selected option?
I have tried using TabLayout, had achieved the centering feature, but wasn't able to implement the snapping feature.
Design part:
<xxx.xxx.xxx.CenteringTabLayout
android:id="#+id/modes"
android:layout_width="match_parent"
android:layout_height="30dp"
android:layout_alignParentBottom="true"
app:tabRippleColor="#android:color/transparent"
app:tabIndicatorFullWidth="false"
app:tabMode="scrolling"
app:tabIndicator="#drawable/mode_indicator"
app:tabGravity="center"
app:tabIndicatorHeight="30dp"
android:background="#android:color/transparent"
android:layout_marginVertical="12dp"
android:layout_marginHorizontal="8dp"/>
CenteringTabLayout.java
package xxx.xxx.xxx;
import android.content.Context;
import android.util.AttributeSet;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
import androidx.camera.extensions.ExtensionMode;
import androidx.core.view.ViewCompat;
import com.google.android.material.tabs.TabLayout;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Objects;
public class CenteringTabLayout extends TabLayout {
private final ArrayList<Integer> snapPoints = new ArrayList<>();
private int count = 0;
public CenteringTabLayout(Context context) {
super(context);
}
public CenteringTabLayout(Context context, AttributeSet attrs) {
super(context, attrs);
}
public CenteringTabLayout(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
}
private int sp = 0;
#Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
super.onLayout(changed, l, t, r, b);
ViewGroup tabParent = (ViewGroup)getChildAt(0);
View firstTab = tabParent.getChildAt(0);
View lastTab = tabParent.getChildAt(tabParent.getChildCount()-1);
sp = (getWidth()/2) - (firstTab.getWidth()/2);
ViewCompat.setPaddingRelative(getChildAt(0), sp,0,(getWidth()/2) - (lastTab.getWidth()/2),0);
View centerTab = tabParent.getChildAt(tabParent.getChildCount()/2);
centerView(centerTab);
count = getTabCount();
snapPoints.clear();
int widthC = 0;
snapPoints.add(0);
for (int i = 0; i < count; ++i) {
View tabView = tabParent.getChildAt(i);
widthC+=tabView.getWidth()/2;
snapPoints.add(widthC + 19);
widthC+=tabView.getWidth()/2;
}
// widthC += tabParent.getChildAt(count-1).getWidth()/2;
snapPoints.add(widthC);
--count;
Log.i("TAG", Arrays.toString(snapPoints.toArray()));
}
private void centerView(View view){
scrollTo(getRelativeLeft(view) - sp - view.getPaddingLeft() , 0);
}
#Override
protected void onScrollChanged(int x, int t, int oldX, int oldT) {
if(Math.abs(oldX-x)<=1) return;
int i = 0;
while(i<count){
final int p = snapPoints.get(i);
final int n = snapPoints.get(++i);
Log.i("i:P,L,N", i+":"+p+","+x+","+n);
if(x>=p && x<=n){
--i;
if(getSelectedTabPosition()==i) return;
View tabView = Objects.requireNonNull(getTabAt(i)).view;
Log.i("Selected", String.valueOf(Objects.requireNonNull(getTabAt(i)).getText()));
tabView.performClick();
centerView(tabView);
return;
}
ExtensionMode;
}
super.onScrollChanged(x, t, oldX, oldT);
}
private int getRelativeLeft(View myView) {
if (myView.getParent() == myView.getRootView())
return myView.getLeft();
else
return myView.getLeft() + getRelativeLeft((View) myView.getParent());
}
}
I have roughly researched for other ways of doing it (using ViewPager + Button/ImageView and FrameLayout, bottom navigation bar, etc.) [not sure if they would fulfil all the requirements though], but does anyone know or could think of better way of implementing it?

You can try and use this library which does something similar to what you require with some incredible animations, but if you want to implement this exact behavior, ViewPager2 is your best option in my opinion, because it has all the features that you require and more, and you can customize it pretty easily.
Update:
For your specific use case, you can do it in a few steps:
Create an adapter for the ViewPager2 - when initializing, pass the list of modes you have as a text. I suggest you create a kind of dictionary with the index of every text value as the key and the text as the value, because to move between pages on click, or start from the middle, you need to call:
pager.setCurrentItem(itemIndex).
Set each page on click listener. See this link for how to do so.
Implement onPageSelcted() callback to show gesture of selecting item and switch between the camera modes. My implementation:
/**
* An extension function that gives a callback for moving between pages in the ViewPager2
*
* #param action A function to execute every time a different page is selected
*/
fun ViewPager2.onPageSelected(action: (Int) -> Unit) {
registerOnPageChangeCallback(object : ViewPager2.OnPageChangeCallback() {
override fun onPageSelected(position: Int) {
super.onPageSelected(position)
action(position)
}
})
}
Initializing the adapter and the view pager:
List<String> modesList = new ArrayList();
modeslist.add("camera");
// todo: add the modes in the order that you want
CustomAdapter adapter = new CustomAdapter(modesList);
pager = (ViewPager2) findViewById(R.id.awesomepager); // Referencing the ViewPager
pager.setAdapter(adapter); // Setting view pager adapter
pager.setCurrentItem(theStartPositionIndex); // Setting the start position
pager.onPageSelected(page -> {
// todo: to what you want when a mode is selected
});
Hope this gives you a rough idea on how to implement your use case.

Imageview parallax as you scroll

I saw many examples demonstrative parallax background as you scroll or listview parallax but I cannot find a clear example how to implement a parallax effect on images as you scroll in the activity.
An example implementation can be found in Airbnb app. As you scroll down you can see more of the image's bottom and as you scroll up you can see more of the image's top.
Any hints and tips on how to create such effect?

There are a few libraries that to a parallax effect, it depends on your app if they are useful for your particular case, for example:
ParallaxScroll
Paralloid
Google is your friend pal ;) if none of these suits your needs then you have to create a custom ScrollView but that's a longer story, first give them a try and post your results.
Edit
If none of these fit your requeriments then this is what you have to do:
First, create a custom ScrollView so you can listen to scroll changes.
public class ObservableScrollView extends ScrollView {
public interface OnScrollChangedListener {
public void onScrollChanged(int deltaX, int deltaY);
}
private OnScrollChangedListener mOnScrollChangedListener;
public ObservableScrollView(Context context) {
super(context);
}
public ObservableScrollView(Context context, AttributeSet attrs) {
super(context, attrs);
}
public ObservableScrollView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
#Override
protected void onScrollChanged(int l, int t, int oldl, int oldt) {
super.onScrollChanged(l, t, oldl, oldt);
if(mOnScrollChangedListener != null) {
mOnScrollChangedListener.onScrollChanged(l - oldl, t - oldt);
}
}
public void setOnScrollChangedListener(OnScrollChangedListener listener) {
mOnScrollChangedListener = listener;
}
}
Obviously you need to use this in your layout instead of the default ScrollView:
<your.app.package.ObservableScrollView
android:id="#+id/scroll_view"
android:layout_width="match_parent"
android:layout_height="match_parent">
Also you need to wrap your ImageView inside a container to make the parallax work:
<FrameLayout
android:id="#+id/img_container"
android:layout_width="match_parent"
android:layout_height="wrap_content" >
<ImageView
android:id="#+id/img"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:scaleType="centerCrop" />
</FrameLayout>
Finally set your Activity as a listener for your brand new ObservableScrollView and let the parallax begin:
public class MyActivity extends Activity implements ObservableScrollView.OnScrollChangedListener {
private ObservableScrollView mScrollView;
private View imgContainer;
#Override
public void onCreate(Bundle savedInstanceState) {
// Init your layout and set your listener
mScrollView = (ObservableScrollView)findViewById(R.id.scroll_view);
mScrollView.setOnScrollChangedListener(this);
// Store the reference of your image container
imgContainer = findViewById(R.id.img_container);
}
#Override
public void onScrollChanged(int deltaX, int deltaY) {
int scrollY = mScrollView.getScrollY();
// Add parallax effect
imgContainer.setTranslationY(scrollY * 0.5f);
}
}
You can modify the 0.5 value depending on how much parallax you want.
Edit
The above answer works fine if your ImageView is in the top of the activity. I am posting some code below to add the functionality to have the ImageView anywhere in the activity layout which I successfully made to work. These are generic calculations (might have some mistakes) and with a little tweak you can have it working for your own case.
For this example I have a fix height for the image container 200dp and for the image 240dp. The main purpose is when the image container is in the middle of the screen have no parallax effect and as the user scroll up or down to apply the effect. So as the image container get closer to the top of the screen or closer to the bottom of the screen the more of the parallax effect will be applied. The following calculations are a little hard to understand by reading them so try to make an example with real numbers in paper.
public class MyActivity extends Activity implements ObservableScrollView.OnScrollChangedListener {
private ObservableScrollView mScrollView;
private View imgContainer;
private ImageView mImageView;
#Override
public void onCreate(Bundle savedInstanceState) {
// Init your layout and set your listener
mScrollView = (ObservableScrollView)findViewById(R.id.scroll_view);
mScrollView.setOnScrollChangedListener(this);
// Store the reference of your image container
imgContainer = findViewById(R.id.img_container);
// Store the reference of your image
mImageView = findViewById(R.id.img);
}
#Override
public void onScrollChanged(int deltaX, int deltaY) {
// Get scroll view screen bound
Rect scrollBounds = new Rect();
mScrollView.getHitRect(scrollBounds);
// Check if image container is visible in the screen
// so to apply the translation only when the container is visible to the user
if (imgContainer.getLocalVisibleRect(scrollBounds)) {
Display display = getWindowManager().getDefaultDisplay();
DisplayMetrics outMetrics = new DisplayMetrics ();
display.getMetrics(outMetrics);
// Get screen density
float density = getResources().getDisplayMetrics().density;
// Get screen height in pixels
float dpHeight = outMetrics.heightPixels / density;
int screen_height_pixels = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dpHeight, getResources().getDisplayMetrics());
int half_screen_height = screen_height_pixels/2;
// Get image container height in pixels
int container_height_pixels = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 200, getResources().getDisplayMetrics());
// Get the location that consider a vertical center for the image (where the translation should be zero)
int center = half_screen_height - (container_height_pixels/2);
// get the location (x,y) of the image container in pixels
int[] loc_screen = {0,0};
imgContainer.getLocationOnScreen(loc_screen);
// trying to transform the current image container location into percentage
// so when the image container is exaclty in the middle of the screen percentage should be zero
// and as the image container getting closer to the edges of the screen should increase to 100%
int final_loc = ((loc_screen[1]-center)*100)/half_screen_height;
// translate the inner image taking consideration also the density of the screen
mImageView.setTranslationY(-final_loc * 0.4f * density);
}
}
}
I hope it can help someone that is looking for similar functionality.

scrollView.getViewTreeObserver().addOnScrollChangedListener(new ViewTreeObserver.OnScrollChangedListener() {
#Override
public void onScrollChanged() {
int top = scrollView.getScrollY(); // Increases when scrolling up ^
if(top != 0) {
int newTop = (int) (top * .5f);
imageFrame.setTop(newTop < 0 ? 0 : newTop);
}
}
});

Paralax effect in app background

Im new in Android world. I want to put some parallax background effects in my app.
How can I do it? How to approach to this in Android?
Is there any productive way to create 2-3 layer parallax background? Is there some tool, or class in android API?
Or maybe I have to modify background image location or margins "manually" in code?
Im using API level 19.
I have tried to understand Paralloid library, but this is too big to understand without any explanation. Im new to Android and Java, im not familiar with all Layouts and other UI objects, however I'm familiar with MVC.
I started bounty, maybe someone can explain step by step how that library works.

This is what you can do:
In your activity/fragment layout file specify 2 ScrollView's (say background_sv and content_sv).
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<com.example.parallax.MyScrollView
android:id="#+id/background_sv"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<ImageView
android:id="#+id/parallax_bg"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="..." />
</com.example.parallax.MyScrollView>
<com.example.parallax.MyScrollView
android:id="#+id/content_sv"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical" >
</LinearLayout>
</com.example.parallax.MyScrollView>
</RelativeLayout>
Add a dummy view in the content scrollview of the height of the background and make it transparent. Now, attach a scroll listener to the content_sv. When the content scrollview is scrolled, call
mBgScrollView.scrollTo(0, (int)(y /*scroll Of content_sv*/ / 2f));
The existing API's doesn't have the support to get the scroll events.
Hence, we need to create a Custom ScrollView, to provide the ScrollViewListener.
package com.example.parallax;
// imports;
public class MyScrollView extends ScrollView {
public interface ScrollViewListener {
void onScrollChanged(MyScrollView scrollView, int x, int y, int oldx, int oldy);
}
private ScrollViewListener scrollViewListener = null;
public MyScrollView(Context context) {
super(context);
}
public MyScrollView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
public MyScrollView(Context context, AttributeSet attrs) {
super(context, attrs);
}
public void setScrollViewListener(ScrollViewListener scrollViewListener) {
this.scrollViewListener = scrollViewListener;
}
#Override
protected void onScrollChanged(int x, int y, int oldx, int oldy) {
super.onScrollChanged(x, y, oldx, oldy);
if(scrollViewListener != null) {
scrollViewListener.onScrollChanged(this, x, y, oldx, oldy);
}
}
}
Here is the activity which hosts both the content ScrollView and background ScrollView
package com.example.parallax;
// imports;
public class ParallaxActivity extends Activity implements ScrollViewListener {
private MyScrollView mBgScrollView;
private MyScrollView mContentScrollView;
#Override
public void onCreate(Bundle savedInstanceState) {
mBgScrollView = findViewById(R.id.background_sv);
mContentScrollView = findViewById(R.id.content_sv);
mContentScrollView.setOnScrollListener(this);
}
// this is method for onScrollListener put values according to your need
#Override
public void onScrollChanged(MyScrollView scrollView, int x, int y, int oldx, int oldy) {
super.onScrollChanged(scrollView, x, y, oldx, oldy);
// when the content scrollview will scroll by say 100px,
// the background scrollview will scroll by 50px. It will
// look like a parallax effect where the background is
// scrolling with a different speed then the content scrollview.
mBgScrollView.scrollTo(0, (int)(y / 2f));
}
}

I think the question is unclear, so this is not really an answer so much as an attempt to clarify with more detail than I could include in a comment.
My question is about what kind of parallax effect you want to achieve. Given these three examples (they are demo apps you can install from the Play Store), which if any has the type of parallax effect you want? Please answer in a comment.
Paralloid Demo
Parallax Scroll Demo
Google IO App
Given an answer, we all will find it easier to help out. If you edit your question to include this information, it will be improved.

The following contains an example application published by the author of Paralloid:
https://github.com/chrisjenx/Paralloid/tree/master/paralloidexample
From the GitHub page under the 'Getting Started' section:
Layout
ScrollView
This is an example, please refer to the paralloidexample App for full
code.
<FrameLayout ..>
<FrameLayout
android:id="#+id/top_content"
android:layout_width="match_parent"
android:layout_height="192dp"/>
<uk.co.chrisjenx.paralloid.views.ParallaxScrollView
android:id="#+id/scroll_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fillViewport="true">
<LinearLayout
android:id="#+id/scroll_content"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
android:paddingTop="192dp"/>
</uk.co.chrisjenx.paralloid.views.ParallaxScrollView>
</FrameLayout>
Fragment
Inside your onViewCreated() or onCreateView().
//...
FrameLayout topContent = (FrameLayout) rootView.findViewById(R.id.top_content);
ScrollView scrollView = (ScrollView) rootView.findViewById(R.id.scroll_view);
if (scrollView instanceof Parallaxor) {
((Parallaxor) scrollView).parallaxViewBy(topContent, 0.5f);
}
// TODO: add content to top/scroll content
Thats it!
Have a look at the Parallaxor interface for applicable Parallax
methods.
Hope this helps!
Also, here is a link to Google's 'getting started' page for android.
Also, here is a link to a 'java tutorial for complete beginners'.
As well as link to some documentation about layouts, which 'define the visual structure for a user interface'.
That being said, you would use the layout to define what the interface looks like and use the subsequent example code to define what happens when you interact with it.
P.S. You can see the application in action here

I use the ParallaxScroll library. Very easy to use, good samples and well documented.

Here is how it can be done using ScrollView and it's background image. I've committed the code in github.
You need to extend the ScrollView and Drawable classes.
By default the ScrollView background height will be same as viewport height. To achieve the parallax effect, the background height should be larger and should be based on the ScrollView child height and the background scrolling factor we want to impose.
Background scroll factor of 1 indicates, background height is same as ScrollView child height and hence background will scroll with same offset as the child scrolls.
0.5 indicates, background height is 0.5 times ScrollView child extended height and will scroll 50% slower compared to the child contents. This effectively brings the parallax scrolling effect.
Call following method from ScrollView constructor:
void init() {
// Calculate background drawable size before first draw of scrollview
getViewTreeObserver().addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
#Override
public boolean onPreDraw() {
// Remove the listener
getViewTreeObserver().removeOnPreDrawListener(this);
mDrawable = (ParallaxDrawable) getBackground();
if(mDrawable != null && mDrawable instanceof ParallaxDrawable) {
// Get the only child of scrollview
View child = getChildAt(0);
int width = child.getWidth();
// calculate height of background based on child height and scroll factor
int height = (int) (getHeight() + (child.getHeight() - getHeight()) * mScrollFactor);
mDrawable.setSize(width, height);
}
return true;
}
});
}
When ScrollView is scrolled, take into consideration the scroll offset while drawing the background. This basically achieves the parallax effect.
ParallaxScrollView:
protected void onScrollChanged(int x, int y, int oldX, int oldY) {
if(mDrawable != null && mDrawable instanceof ParallaxDrawable) {
// set the scroll offset for the background drawable.
mDrawable.setScrollOffset(x*mScrollFactor, y*mScrollFactor);
}
}
ParallaxDrawable:
#Override
public void draw(Canvas canvas) {
// To move the background up, translate canvas by negative offset
canvas.translate(-mScrollXOffset, -mScrollYOffset);
mDrawable.draw(canvas);
canvas.translate(mScrollXOffset, mScrollYOffset);
}
protected void onBoundsChange(Rect bounds) {
// This sets the size of background drawable.
mDrawable.setBounds(new Rect(bounds.top, bounds.left, bounds.left + mWidth, bounds.top + mHeight));
}
Usage of ParallaxScrollView and ParallaxDrawable:
public class MyActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.parallax_layout);
final ParallaxScrollView scrollView = (ParallaxScrollView) findViewById(R.id.sv);
ParallaxDrawable drawable = new ParallaxDrawable(getResources().getDrawable(R.drawable.bg));
scrollView.setBackground( drawable, 0.2f );
}
}
parallax_layout.xml:
<manish.com.parallax.ParallaxScrollView
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/sv"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<TextView
android:id="#+id/tv"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textColor="#fff"
android:text="#string/text" />
<View
android:layout_width="match_parent"
android:layout_height="5dp" />
...
</LinearLayout>
</manish.com.parallax.ParallaxScrollView>

The Android API does not support much concrete tools for it as you probably noticed. In API 20 they added elevation which is an attribute for depth. This does not support parallax layouts itself but I would say it's a step by Google to make this kind of work easier. If you want a wild guess on if and when, I would say that parallax utilities could be added before API 25 is released, based on the latest update and the progress in battery efficiency.
For now all you need is to listen for some kind of movement and change the views positions based on a value representing elevation.
Your question made me upgrade my own project and this is how I did it using ViewDragHelper inside a Fragment.
public class MainFragment extends Fragment implements View.OnTouchListener {
private ImageView mDecor, mBamboo, mBackgroundBamboo;
private RelativeLayout mRootLayout;
private ViewDragHelper mDragHelper;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
mRootLayout = (RelativeLayout) inflater.inflate(R.layout.fragment_main, container, false);
mRootLayout.setOnTouchListener(this);
mDecor = (ImageView) mRootLayout.findViewById(R.id.decor);
mBamboo = (ImageView) mRootLayout.findViewById(R.id.bamboo);
mBackgroundBamboo = (ImageView) mRootLayout.findViewById(R.id.backround_bamboo);
mDragHelper = ViewDragHelper.create(mRootLayout, 1.0f, new ViewDragHelper.Callback() {
private final float MAX_LEFT = -0;
private final float MAX_TOP = -20;
private final float MAX_RIGHT = 50;
private final float MAX_BOTTOM = 10;
private final float MULTIPLIER = 0.1f;
private final int DECOR_ELEVATION = 3;
private final int FRONT_BAMBOO_ELEVATION = 6;
private final int BACKGROUND_BAMBOO_ELEVATION = 1;
private float mLeft = 0;
private float mTop = 0;
#Override
public boolean tryCaptureView(View view, int i) {
return true;
}
#Override
public int clampViewPositionVertical(View child, int top, int dy) {
mTop += dy * MULTIPLIER;
mTop = mTop > MAX_BOTTOM ? MAX_BOTTOM : mTop < MAX_TOP ? MAX_TOP : mTop;
mDecor.setTranslationY(mTop * DECOR_ELEVATION);
mBamboo.setTranslationY(mTop * FRONT_BAMBOO_ELEVATION);
mBackgroundBamboo.setTranslationY(mTop * BACKGROUND_BAMBOO_ELEVATION);
return 0;
}
#Override
public int clampViewPositionHorizontal(View child, int left, int dx) {
mLeft += dx * MULTIPLIER;
mLeft = mLeft < MAX_LEFT ? MAX_LEFT : mLeft > MAX_RIGHT ? MAX_RIGHT : mLeft;
mDecor.setTranslationX(mLeft * DECOR_ELEVATION);
mBamboo.setTranslationX(mLeft * FRONT_BAMBOO_ELEVATION);
mBackgroundBamboo.setTranslationX(mLeft * BACKGROUND_BAMBOO_ELEVATION);
return 0;
}
#Override
public void onViewPositionChanged(View changedView, int left, int top, int dx, int dy){
mRootLayout.requestLayout();
}
});
return mRootLayout;
}
#Override
public boolean onTouch(View view, MotionEvent motionEvent) {
mDragHelper.processTouchEvent(motionEvent);
// you can still use this touch listener for buttons etc.
return true;
}
}

Hi You can go with the below-given code for ParallaxView class
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Rect;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import java.util.ArrayList;
public class ParallaxView extends SurfaceView implements Runnable {
private volatile boolean running;
private Thread gameThread = null;
// For drawing
private Paint paint;
private Canvas canvas;
private SurfaceHolder ourHolder;
// Holds a reference to the Activity
Context context;
// Control the fps
long fps =60;
// Screen resolution
int screenWidth;
int screenHeight;
ParallaxView(Context context, int screenWidth, int screenHeight) {
super(context);
this.context = context;
this.screenWidth = screenWidth;
this.screenHeight = screenHeight;
// Initialize our drawing objects
ourHolder = getHolder();
paint = new Paint();
}
#Override
public void run() {
while (running) {
long startFrameTime = System.currentTimeMillis();
update();
draw();
// Calculate the fps this frame
long timeThisFrame = System.currentTimeMillis() - startFrameTime;
if (timeThisFrame >= 1) {
fps = 1000 / timeThisFrame;
}
}
}
private void update() {
// Update all the background positions
}
private void draw() {
if (ourHolder.getSurface().isValid()) {
//First we lock the area of memory we will be drawing to
canvas = ourHolder.lockCanvas();
//draw a background color
canvas.drawColor(Color.argb(255, 0, 3, 70));
// Draw the background parallax
// Draw the rest of the game
paint.setTextSize(60);
paint.setColor(Color.argb(255, 255, 255, 255));
canvas.drawText("I am a plane", 350, screenHeight / 100 * 5, paint);
paint.setTextSize(220);
canvas.drawText("I'm a train", 50, screenHeight / 100*80, paint);
// Draw the foreground parallax
// Unlock and draw the scene
ourHolder.unlockCanvasAndPost(canvas);
}
}
// Clean up our thread if the game is stopped
public void pause() {
running = false;
try {
gameThread.join();
} catch (InterruptedException e) {
// Error
}
}
// Make a new thread and start it
// Execution moves to our run method
public void resume() {
running = true;
gameThread = new Thread(this);
gameThread.start();
}
}// End of ParallaxView
To know more you can go **
here
**: http://gamecodeschool.com/android/coding-a-parallax-scrolling-background-for-android/

Grid of images inside ScrollView

I'm trying to create a screen with both text and images. I want the images to be laid out like a grid, as shown below, but I want them to have no scroll functionality other that the one provided by the surrounding ScrollView.
An image will best illustrate my question:
<ScrollView>
<LinearLayout>
<ImageView />
<TextView />
<GridView />
<TextView />
</LinearLayout>
</ScrollView>
What is the best way to make show a grid of a varying number of images, where the grid does not have scroll functionality?
Please note that disabling the scroll functionality for the GridView does not work, as this just disables the scrollbars but does not show all items.
Update:
The image below shows what it looks like with scrollbars disabled in the GridView.

Oh boy, yeah, you're gonna have trouble with this one. It drives me nuts that ListViews and GridViews can't be expanded to wrap their children, because we all know that they have more beneficial features in addition to their scrolling and the recycling of their children.
Nonetheless, you can hack around this or create your own layout to suit your needs without too much difficulty. Off the top of my head, I can think of two possibilities:
In my own app I have embedded a ListView within a ScrollView. I have done this by explicitly telling the ListView to be exactly as high as its contents. I do it by changing the layout parameters right inside the ListView.onMeasure() method like so:
public class ExpandableListView extends ListView {
boolean expanded = false;
public ExpandableListView(Context context, AttributeSet attrs, int defaultStyle) {
super(context, attrs, defaultStyle);
}
public boolean isExpanded() {
return expanded;
}
public void setExpanded(boolean expanded) {
this.expanded = expanded;
}
#Override
public void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
// HACK! TAKE THAT ANDROID!
if (isExpanded()) {
// Calculate entire height by providing a very large height hint.
// View.MEASURED_SIZE_MASK represents the largest height possible.
int expandSpec = MeasureSpec.makeMeasureSpec(MEASURED_SIZE_MASK,
MeasureSpec.AT_MOST);
super.onMeasure(widthMeasureSpec, expandSpec);
LayoutParams params = getLayoutParams();
params.height = getMeasuredHeight();
} else {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}
}
}
This works because when you give the ListView a mode of AT_MOST, it creates and measures all of its children for you, right inside the onMeasure method (I discovered this by browsing through the source code). Hopefully GridView behaves the same, but if it doesn't, you can still measure all the contents of the GridView yourself. But it would be easier if you could trick the GridView into doing it for you.
Now, you must keep in mind that this solution would completely disable the view recycling that makes GridView so efficient, and all those ImageViews will be in memory even if they're not visible. Same goes with my next solution.
The other possibility is to ditch the GridView and create your own layout. You could extend either AbsoluteLayout or RelativeLayout. For example, if you extend RelativeLayout, you could place each image LEFT_OF the previous one, keeping track of the width of each image until you run out of room on that row, and then start the next row by placing the first image of the new row BELOW the tallest image of the last row. To get the images horizontally centered or in equally-spaced columns you'll have to go through even more pain. Maybe AbsoluteLayout is better. Either way, kind of a pain.

A GridView with header and footer can be used instead of trying to embed GridView in ScrollView. Header and footer can be anything - texts, images, lists, etc. There is an example of GridView with header and footer: https://github.com/SergeyBurish/HFGridView

You have 2 solutions for this one:
Write your own custom layout. This would be the harder solution (but might be considered the correct one).
Set the real height of your GridView in the code. For example:
RelativeLayout.LayoutParams lp = (RelativeLayout.LayoutParams) myGridView.getLayoutParams();
// lp.setMargins(0, 0, 10, 10); // if you have layout margins, you have to set them too
lp.height = measureRealHeight(...);
myGridView.setLayoutParams(lp);
The measureRealHeight() method should look something like this (hopefully I got it right):
private int measureRealHeight(...)
{
final int screenWidth = getWindowManager().getDefaultDisplay().getWidth();
final double screenDensity = getResources().getDisplayMetrics().density;
final int paddingLeft = (int) (X * screenDensity + 0.5f); // where X is your desired padding
final int paddingRight = ...;
final int horizontalSpacing = (int) (X * screenDensity + 0.5f); // the spacing between your columns
final int verticalSpacing = ...; // the spacing between your rows
final int columnWidth = (int) (X * screenDensity + 0.5f);
final int columnsCount = (screenWidth - paddingLeft - paddingRight + horizontalSpacing - myGridView.getVerticalScrollbarWidth()) / (columnWidth + horizontalSpacing);
final int rowsCount = picsCount / columnsCount + (picsCount % columnsCount == 0 ? 0 : 1);
return columnWidth * rowsCount + verticalSpacing * (rowsCount - 1);
}
The above code should work in Android 1.5+.

Create a non scrollable list view like this:
public class ExpandableListView extends ListView{
public ExpandableListView(Context context) {
super(context);
}
public ExpandableListView(Context context, AttributeSet attrs, int defaultStyle) {
super(context, attrs, defaultStyle);
}
public ExpandableListView(Context context, AttributeSet attrs) {
super(context, attrs);
}
#Override
public void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
int heightMeasureSpec_custom = MeasureSpec.makeMeasureSpec(
Integer.MAX_VALUE >> 2, MeasureSpec.AT_MOST);
super.onMeasure(widthMeasureSpec, heightMeasureSpec_custom);
ViewGroup.LayoutParams params = getLayoutParams();
params.height = getMeasuredHeight();
}
}
In your layout file create an element like this:
<com.example.ExpandableListView
android:layout_width="match_parent"
android:layout_height="wrap_content"/>
This should work.

I found a way to give the GridView a fixed size inside ScrollView, and enable scrolling it.
To do so, you would have to implement a new class extending GridView and override onTouchEvent() to call requestDisallowInterceptTouchEvent(true).
Thus, the parent view will leave the Grid intercept touch events.
GridViewScrollable.java:
package com.example;
import android.content.Context;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.widget.GridView;
public class GridViewScrollable extends GridView {
public GridViewAdjuntos(Context context) {
super(context);
}
public GridViewAdjuntos(Context context, AttributeSet attrs) {
super(context, attrs);
}
public GridViewAdjuntos(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
#Override
public boolean onTouchEvent(MotionEvent ev){
// Called when a child does not want this parent and its ancestors to intercept touch events.
requestDisallowInterceptTouchEvent(true);
return super.onTouchEvent(ev);
}
}
Add it in your layout with the characteristics you want:
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:isScrollContainer="true" >
<com.example.GridViewScrollable
android:id="#+id/myGVS"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:clickable="true"
android:numColumns="auto_fit"
android:columnWidth="100dp"
android:stretchMode="columnWidth" />
</ScrollView>
And just get it in your activity and set the adapter, for example an ArrayAdapter<>:
GridViewScrollable mGridView = (GridViewScrollable) findViewById(R.id.myGVS);
mGridView.setAdapter(new ArrayAdapter<>(this, android.R.layout.simple_list_item_1, new String[]{"one", "two", "three", "four", "five"}));
I hope it helps =)

Try this
public static void setGridViewHeightBasedOnChildren(GridView gridView, int columns) {
ListAdapter listAdapter = gridView.getAdapter();
if (listAdapter == null)
return;
int desiredWidth = View.MeasureSpec.makeMeasureSpec(gridView.getWidth(), View.MeasureSpec.UNSPECIFIED);
int totalHeight = 0;
View view = null;
int rows = listAdapter.getCount() / columns;
if(listAdapter.getCount() % columns> 0){
rows++;
}
for (int i = 0; i < rows; i++) {
view = listAdapter.getView(i, view, gridView);
if (i == 0)
view.setLayoutParams(new ViewGroup.LayoutParams(desiredWidth, LinearLayout.LayoutParams.WRAP_CONTENT));
view.measure(desiredWidth, View.MeasureSpec.UNSPECIFIED);
totalHeight += view.getMeasuredHeight();
}
ViewGroup.LayoutParams params = gridView.getLayoutParams();
params.height = totalHeight + (gridView.getHorizontalSpacing() * rows);
gridView.setLayoutParams(params);
gridView.requestLayout();
}

For GridView with other View inside of the save ScrollView to make it all scroll, go to this link: http://www.londatiga.net/it/programming/android/make-android-listview-gridview-expandable-inside-scrollview/#comment-3967742. It is helpful and have saved my time which I just spend 5 minute with this when I have never know about it.
Update:
From the link I have customize an ExpandedGridView:
public class ExpandedGridView extends GridView {
boolean expanded = false;
public ExpandedGridView(Context context) {
super(context);
}
public ExpandedGridView(Context context, AttributeSet attrs) {
super(context, attrs);
}
public ExpandedGridView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
public boolean isExpanded() {
return expanded;
}
#Override
public void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
// HACK! TAKE THAT ANDROID!
if (isExpanded()) {
// Calculate entire height by providing a very large height hint.
// But do not use the highest 2 bits of this integer; those are
// reserved for the MeasureSpec mode.
int expandSpec = MeasureSpec.makeMeasureSpec(Integer.MAX_VALUE >> 2, MeasureSpec.AT_MOST);
super.onMeasure(widthMeasureSpec, expandSpec);
ViewGroup.LayoutParams params = getLayoutParams();
params.height = getMeasuredHeight();
} else {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}
}
public void setExpanded(boolean expanded) {
this.expanded = expanded;
}
}
For your xml change from GridView to the ExpandedGridView which have been customized.
<com.your.package.ExpandedGridView
android:id="#+id/home_screen_list_goals"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:numColumns="2" />
Usage:
Call it in your activity. If in fragment use contentView.findViewById(...). Which contentView is your whole layout defined.
ExpandedGridView gridView = (ExpandedGridView) findViewById(R.id.home_screen_list_goals);
//set data into grid view
gridView.setAdapter(YOUR_ADAPTER_OBJECT);
gridView.setExpanded(true);

In ListView Which function is called while scrolling

public class SynchronisedScrollView extends ListView {
private ScrollViewListener scrollViewListener = null;
public SynchronisedScrollView(Context context) {
super(context);
}
public SynchronisedScrollView(Context context, AttributeSet attrs,
int defStyle) {
super(context, attrs, defStyle);
}
public SynchronisedScrollView(Context context, AttributeSet attrs) {
super(context, attrs);
}
#Override
protected void onScrollChanged(int x, int y, int oldx, int oldy) {
Log.d("Hello", "I am scrolled");
// super.onScrollChanged(x, y, oldx, oldy);
}
}
I want to catch how much the listView is scrolled, so I extend ListView. I am able to scroll the list. But OnScrollChanged is not called. For ScrollView and HorizontalScrollView OnScrollChanged is called whenever it scrolls. Which function is triggered when we scroll a ListView.

In ListView you must explicitly register an onScrollListener to receive onScroll() events.

I think that the method you are looking for is:
public void offsetChildrenTopAndBottom(int offset) {
// ...
}
from ViewGroup. What you can do is extend ListView to gather the offset given to one of the ListViews and pass it though to the other ListView. Make sure that you call super.offsetChildrenTopAndBottom on the recieven end or you could easily end up with a stackoverflow.
I would create a private method and have the new Observable views.
public class ObservableListView extends ListView {
private ObservableListView peer;
// [Constructors] make sure you override all the super constructors.
// Can have trouble with layouts otherwise
public void setPeer(ObservableListView peer) {
this.peer = peer;
}
#Override
public void offsetTopAndBottom(int offset) {
super.offsetTopAndBottom(offset);
if (peer != null) {
peer.internalVerticalOffset(offset);
}
}
private void internalVerticalOffset(int offset) {
super.offsetTopAndBottom(offset);
}
}
If you feel brave you can also define an xml property to give one of the ListViews id and let that one set up the peer relation. (I can expand if you are interested)
My bad, this is non working code. I'm trying to figure out how to do this with the hidden method. In this code I'm overriding the wrong method. Will update shortly.
Update:
Ok, after some research I think that the best option is to combine the extension of ListView with a TouchDelegate.