Develop Reference

Drawing background on TextView (not on its full width)

I would like to set a background drawable (or resource) on a TextView, not taking into account its compound drawable width (and paddings).
Getting the width of the compound (left one to be more precise), and its paddings should not be a problem, but the setting of the background on the width of the textview minus the width of the compound drawable (described above).
Should you have any advice on doing that, please let me know.
Here's the needed result:
PS. I thought about having a horizontal LinearLayout with an ImageView and TextView as its children, and having the background set on the textview only, but I am interested in having the same result with less Views (in this case, exactly one), if it is possible.

You could use a LayerDrawable which supports insets, for example:
<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
<item android:left="dimension" android:right="dimension">
<shape android:shape="rectangle">
<solid android:color="color" />
</shape>
</item>
</layer-list>
If you want to change your Drawable dynamically you're better off writing your own Drawable class. The following DividerDrawable for instance draws a line to a given padding onto a white background:
public class DividerDrawable extends Drawable {
private Paint mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
private float mDensity;
private int mPaddingLeft = 0;
public DividerDrawable(Context context) {
mPaint.setColor(Color.BLACK);
mDensity = context.getResources().getDisplayMetrics().density;
}
#Override
public void draw(Canvas canvas) {
int width = canvas.getWidth();
int height = canvas.getHeight();
canvas.drawColor(Color.WHITE);
canvas.drawRect(mPaddingLeft, height - mDensity, width, height, mPaint);
}
#Override
public void setAlpha(int alpha) {
}
#Override
public void setColorFilter(ColorFilter colorFilter) {
}
#Override
public int getOpacity() {
return PixelFormat.TRANSLUCENT;
}
public void setPaddingLeft(int paddingLeft) {
if (mPaddingLeft != paddingLeft) {
mPaddingLeft = paddingLeft;
invalidateSelf();
}
}
}
To set the left padding based on your left CompoundDrawable you could do something like this:
private void setBackground(TextView textView, DividerDrawable background) {
Drawable drawableLeft = textView.getCompoundDrawables()[0];
int paddingLeft = drawableLeft != null ?
textView.getPaddingLeft() + drawableLeft.getIntrinsicWidth() + textView.getCompoundDrawablePadding() :
textView.getPaddingLeft();
background.setPaddingLeft(paddingLeft);
textView.setBackground(background);
}
To make good use of all this call it like so:
DividerDrawable dividerDrawable = new DividerDrawable(this);
TextView textView = (TextView) findViewById(R.id.text);
setBackground(textView, dividerDrawable);

Stuttering Animation

I wrote an application which has an Image which fit to the whole screen.
The Image.resource is a png with the size 768x1024 pixel.
<ImageView
android:id="#+id/imgage1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:scaleType="fitXY"
android:src="#drawable/imagepng" />
The code to animate this Imageview is as follows:
public void animate(int percent) {
height = imgage1.getMeasuredHeight()/100;
ObjectAnimator anim = ObjectAnimator.ofFloat(ActivityMain.this.imgage1, "translationY",ActivityMain.this.imgage1.getTranslationY(), - (percent*height));
ObjectAnimator.setFrameDelay(24);
anim.setDuration(5000);
anim.setInterpolator(new AccelerateDecelerateInterpolator());
anim.start();
}
unfortunately the animation stutters. I thought this stuttering comes from the scaletype "fitXY" because on every animationstepp the Imageview scales the png.
What can I do if I want to use fitXY with one PNG for all Windowsizes to eleminate the stuttering

Meanwhile I have found the reason why the animation is stuttering:
Because the scaletype of the Imageview is set to fitXY, the system renders on each frame a new scaled bitmap, that costs much performance.
So I dont attach the Bitmap by XML to the Imageview,. This work is done by a ncustom ImageView-Class:
public class CustomImageView extends ImageView {
Bitmap bitmapScaled;
Bitmap bitmapOrg;
public CustomImageView (Context context,AttributeSet attr) {
super(context,attr);
Resources mRes = context.getResources();
bitmapOrg = BitmapFactory.decodeResource(mRes, R.drawable.thepng);
}
#Override
protected void onDraw(Canvas canvas){
super.onDraw(canvas);
canvas.drawBitmap(bitmapScaled,0, 0, null);
}
#Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec){
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
if(bitmapScaled == null) {
bitmapScaled = Bitmap.createScaledBitmap(bitmapOrg,getMeasuredWidth(),getMeasuredHeight(),true);
}
}
}

Android:Why after override onMeasure() in a custom view, the view's text can't show in RalativeLayout?

I made a custom component that extends View and overrides its onMeasure(), the content of this component is some text, then I add it to a RelativeLayout, but this text can't display, if I comment onMeasure() that been overridden the text shows. What's the reason?
Here is the code:
public class CustomView extends View {
private String text;
private int viewWidth;
private int viewHeight;
private Paint paint;
private FontMetrics fontMetrics;
public CustomView(Context context) {
this(context, null);
}
public CustomView(Context context, String text) {
this(context, text, 0);
this.text = text;
paint = new Paint(Paint.ANTI_ALIAS_FLAG);
updateViewBounds();
}
public CustomView(Context context, String text, int defStyle) {
super(context);
}
private void updateViewBounds(){
viewWidth = (int) paint.measureText(this.text);
fontMetrics = paint.getFontMetrics();
viewHeight = (int)(fontMetrics.descent - fontMetrics.ascent);
}
private String getText() {
return this.text;
}
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
setMeasuredDimension(viewWidth, viewHeight);
//setMeasuredDimension(560, 100);even though give a ensured size, it can't //anyway.
}
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
paint.setColor(Color.WHITE);
paint.setTextSize(30);
canvas.drawText(text, 0, 200, paint);
Log.e("content", ""+this.getText());
}
public boolean onTouchEvent (MotionEvent event){
Log.e("Touch", ""+this.getText());
return false;
}
}
Here is the Activity:
public class CustomViewActivity extends Activity {
/** Called when the activity is first created. */
private RelativeLayout contentLayout;
private CustomView view1;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
contentLayout = (RelativeLayout)findViewById(R.id.contentLayout);
view1 = new CustomView(this, "You drive me crazy!!!");
RelativeLayout.LayoutParams layoutParams = new RelativeLayout.LayoutParams(
LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
view1.setLayoutParams(layoutParams);
contentLayout.addView(view1);
}
}
this is the XML file:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/contentLayout"
android:layout_width="1024px"
android:layout_height="560px"
android:orientation="vertical" >
<Button
android:id="#+id/button2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_alignParentLeft="true"
android:layout_marginLeft="126dp"
android:text="Button" />
</RelativeLayout>

You can absolutely set the MeasureSpec to a different size, however, the arguments for onMeasure are misleading. A MeasureSpec is a specially translated int that has to be specifically created by using both a pixel measure and a flag. The correct way to set a specific size it indicated below...
final int desiredHSpec = MeasureSpec.makeMeasureSpec(pixelHeight, MeasureSpec.MODE_CONSTANT);
final int desiredWSpec = MeasureSpec.makeMeasureSpec(pixelWidth, MeasureSpec.MODE_CONSTANT);
setMeasuredDimension(desiredWSpec, desiredHSpec);
The MODE_CONSTANTS must have a value of one of the following:
* AT_MOST - meaning that it is dynamic, but will be clipped if the contents are too large
* EXACTLY - meaning it will be that size no matter how large or small the contents are
* UNSPECIFIED - meaning that it will make whatever decision it makes according to the parameters of the parents, children, device size, etc...
If you do not specify one of these constants, then the Android Layout rendering engine has no idea what to do, and simply hides the object. It must be understood, that as an open platform for so many devices, Google decided to make the layout engine "dynamic and intelligent" to support as many apps as possible on as many platforms as possible. This simply requires the developer to let the device know exactly what it needs.
Note: It sounds like you want EXACTLY, but think carefully about your choice and how many devices you will be supporting. :)

Scale image within custom ImageView

I'm extending ImageView in order to manually scale an image within the view. I want to scale an image to fill the width of the custom view, and then draw it to the canvas, however, I'm unable to get the view width using this.getWidth()
It just returns 0, as the view has not yet been drawn and so has dimensions 0 by 0.
Currently I have the following in my main.xml:
<com.android.myapp.BackgroundView
android:id="#+id/background_view"
android:layout_height="fill_parent"
android:layout_width="fill_parent"
android:src="#drawable/background"
android:dither="true"
/>
The custom class is as follows:
public class BackgroundView extends ImageView {
private Paint paint;
private Bitmap background;
public BackgroundView(Context context) {
super(context);
paint = new Paint();
loadBitmap();
}
public BackgroundView(Context context, AttributeSet attrs) {
super(context, attrs);
paint = new Paint();
loadBitmap();
}
public void loadBitmap() {
BitmapDrawable src = (BitmapDrawable) this.getDrawable();
background = src.getBitmap();
}
#Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
canvas.drawBitmap(background, 0, 0, paint);
}
#Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}
}
My Main.java class is:
public class Main extends Activity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}
I can't use
Bitmap.createScaledBitmap(background, view.getWidth(), view.getHeight(), false)
as the view hasn't yet been drawn, how would I go about scaling the image to fill the view/screen width at this point?
Thanks in advance.

I believe what you want to do could also be achieved by using ImageView directly in conjunction with the scaleType attribute. Either use fitXY or centerCrop, depending on your needs.
But to answer the question, you can only use getWidth() and getHeight() after layout() has been called. So you should be able to use the values inside your onDraw method.
Also you could use another drawBitmap method so you wouldn't have to create a new bitmap in memory.

programmatically darken a View android

I found how to change the opacity of a View, but I need to actually darken a View. My best idea is to put a transparent black rectangle over it and then slowly increase the opacity of the rectangle.
Do you know a nicer way to do it?
public class Page07AnimationView extends ParentPageAnimationView {
private final String TAG = this.getClass().getSimpleName();
private ImageView overlay;
private int mAlpha = 0;
public Page07AnimationView(Context context) {
super(context);
}
public Page07AnimationView(Context context, AttributeSet attrs) {
super(context, attrs);
}
protected void init()
{
overlay = new ImageView(mContext);
overlay.setImageResource(R.drawable.black_background);
overlay.setAlpha(0);
overlay.setWillNotDraw(false);
// make the PageAniSurfaceView focusable so it can handle events
setFocusable(true);
}
protected void draw_bitmaps(Canvas canvas)
{
overlay.draw(canvas);
update_bitmaps();
invalidate();
}
public void update_bitmaps()
{
if(mAlpha < 250)
{
mAlpha += 10;
overlay.setAlpha(mAlpha);
}
}
}
The code above isn't doing what I had hoped. Page07AnimationView is added to a FrameLayout over the view I need to darken. R.drawable.black_background points to a 787px x 492px black png image.
I added overlay.setWillNotDraw(false); but it didn't help.
I changed the first setAlpha(0) to setAlpha(255) but that didn't help.
I removed the setAlpha() calls altogether, but it didn't help.
This basic technique of adding a PageNNAnimationView has been working to draw Bitmaps, but not to draw ImageView overlay. (I would use Bitmaps, but they don't seem to have an alpha component.)
Edit2: this is the parent of the class above:
public class ParentPageAnimationView extends View {
private final String TAG = this.getClass().getSimpleName();
protected Context mContext;
public ParentPageAnimationView(Context context) {
super(context);
mContext = context;
init();
}
public ParentPageAnimationView(Context context, AttributeSet attrs) {
super(context, attrs);
mContext = context;
init();
}
protected void init()
{
}
protected void draw_bitmaps(Canvas canvas)
{
// will be overridden by child classes
}
#Override
protected void onDraw(Canvas canvas) {
if(this.getVisibility() == View.VISIBLE)
{
if(canvas != null)
{
draw_bitmaps(canvas);
}
}
}
public void update_bitmaps()
{
// will be overridden by child classes
}
public void elementStarted(PageElement _pageElement) {
// Nothing in parent class
}
public void elementFinished(PageElement mElement) {
// Nothing in parent class
}
}

In case of an ImageView, here's one way to achieve it:
imageView.setColorFilter(Color.rgb(123, 123, 123), android.graphics.PorterDuff.Mode.MULTIPLY);

I would rather do it in the opposite way - put a dark rectangle behind the view and set the view's opacity. This saves painting the rectangle when the view is 100% opaque.

I would do something like this:
view.getBackground().setColorFilter(color, PorterDuff.Mode.DARKEN);
Use black color with some alpha like 0x7f000000 for a typical darkening.
It's more concise and you can also darken the View with animation or scrolling event for example. Just set Color.argb(alpha, 0, 0, 0) as the color and animate alpha, or change it based on the scrolling offset.

This is how I ended up doing it. The key was to use a Paint with its alpha set to whatever I wanted.
public class Page07AnimationView extends ParentPageAnimationView {
private final String TAG = this.getClass().getSimpleName();
private Bitmap bitmap;
private BitmapDrawable drawable;
private ImageView overlay;
private int which = -1;
private long last_time;
private Page07State state;
private int mAlpha;
private int maxAlpha;
private Paint mPaint;
private int _alpha_step;
private int minAlpha;
public enum Page07State {
WAITING, DARKENING, DARKENED
}
public Page07AnimationView(Context context) {
super(context);
}
public Page07AnimationView(Context context, AttributeSet attrs) {
super(context, attrs);
}
protected void init()
{
minAlpha = 0;
mAlpha = minAlpha;
_alpha_step = 5;
maxAlpha = 255;
mPaint = new Paint();
mPaint.setAlpha(minAlpha);
state = Page07State.WAITING;
overlay = new ImageView(mContext);
overlay.setImageResource(R.drawable.black_background);
drawable = (BitmapDrawable) overlay.getDrawable();
bitmap = drawable.getBitmap();
last_time = 0;
}
protected void draw_bitmaps(Canvas canvas)
{
if(state != Page07State.WAITING)
{
DebugLog.d(TAG, "drawing " + Integer.toString(which));
canvas.drawBitmap(bitmap, 0, 0, mPaint);
}
update_bitmaps();
invalidate();
}
public void update_bitmaps()
{
if(state == Page07State.DARKENING)
{
if(mAlpha < maxAlpha)
{
if(System.currentTimeMillis() > last_time + 12)
{
last_time = System.currentTimeMillis();
mAlpha += _alpha_step;
mPaint.setAlpha(mAlpha);
}
}
else
{
state = Page07State.DARKENED;
}
}
}
public void runAnimation()
{
state = Page07State.DARKENING;
}
}

Adding to android developer's answer:
imageView.setColorFilter(Color.rgb(123, 123, 123), android.graphics.PorterDuff.Mode.MULTIPLY);
you can setColorFilter on any view like this:
GradientDrawable gd = (GradientDrawable) textView.getBackground();
gd.setColor(color); //you can also set BG color to a textview like this
gd.setColorFilter(Color.rgb(123, 123, 123), android.graphics.PorterDuff.Mode.MULTIPLY);

you could try using the Alpha animation like this (perhaps on the rectangle):
Animation animation = new AlphaAnimation(0.0f, 1.0f);
animation.setDuration(350);
That would cause the rectangle to gradually become opaque over 350 seconds...

Android actually exposes a drawable which can be used to darken views. You can easily attach it to any view with an Overlay.
Here are two extension functions which can be used to darken any view.
fun View.darken() {
val darkOverlay = ResourcesCompat.getDrawable(
resources,
android.R.drawable.screen_background_dark_transparent,
context.theme
)!!.mutate() // We mutate the drawable so we can later implement a fade in/out animation and animate the Drawable's alpha property. Since Drawables share their state we need to mutate otherwise we would impact all instances of this drawable
darkOverlay.setBounds(0, 0, width, height)
setTag(R.id.dark_overlay, darkOverlay)
overlay.add(darkOverlay)
}
fun View.lighten() {
(getTag(R.id.dark_overlay) as? Drawable)?.let {
overlay.remove(it)
setTag(R.id.dark_overlay, null)
}
}
Make sure you add the id to ids.xml
<?xml version="1.0" encoding="utf-8"?>
<resources>
<item name="dark_overlay" type="id" />
</resources>
And if you're darkening your application's root layout and would like to darken the NavigationBar as well, you might need to add the the following to your theme in styles.xml
<style name="BaseTheme" parent="Theme.MaterialComponents.DayNight.NoActionBar">
<!-- required for api 29 otherwise the system will set a white background color to the NavigationBar to ensure the buttons are visible -->
<item name="android:enforceNavigationBarContrast">false</item>
<item name="android:windowDrawsSystemBarBackgrounds">true</item>
</style>

You should check iPaulPro's answer in this question. You will need to extend ImageView and override the onDraw() method.
Depending on what you are going to do, Alexandru Cristescu's answer is also valid but you should
call setFillAter(true) for the animation to persist after finished.