I want to create a layer with transparent layer over an activity and I need to make visible only a particular view, say for an example "Login Button". It something mean that making hole on layer exactly the size of the button. Please anyone help me out of this.
Thanks In advance.
Programatically, you can use Canvas to create a layer. Fill the whole thing with your color and cut out a hole.
public class DrawView extends View {
Paint paint = new Paint();
Paint transparentPaint = new Paint;
public DrawView(Context context) {
super(context);
}
#Override
public void onDraw(Canvas canvas) {
//first fill everything with your covering color
paint.setColor(yourTransparentColor);
canvas.drawRect(0, 0, canvas.getWidth(), canvas.getHeight(), paint);
//now clear out the area you want to see through
transparentPaint.setAlpha(0xFF);
transparentPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
Rect rect=new Rect(left, top, right, bottom);//make this your rect!
canvas.drawRect(rect,transparentPaint);
}
}
If I understand your question correctly
Your parent Layout of the Activity will be a RelativeLayout. In your parent layout at the bottom add another child RelativeLayout that implments the match_parent parameters for both width and height. You can then set a color like this #99000000 to it's background. This will give you a black transparent layer over your parent.
Something like this
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/parentLayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#FFFFFF">
<!-- here you add your activities views ect... -->
<RelativeLayout
android:id="#+id/childLayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#99000000">
<!-- This will be your overlay so here you can add your login button ect -->
</RelativeLayout>
</RelativeLayout>
I didn't test this but it should solve your issue
On following "HalR" Steps , I was able to achieve the transparent background Thanks to him and found some of you are getting pitch black on the cut made over transparent layer is due to Graphic rendering . that can be enabled using below code inside onDraw method
` #Override
public void onDraw(Canvas canvas) {
if (android.os.Build.VERSION.SDK_INT >= 11) {
setLayerType(View.LAYER_TYPE_SOFTWARE, null);
}
.....
..... // your draw rect creation and other stuff `
which will let you have the transparent area by eliminating the Pitch black color
If i understood your question then this is what you wanted:
You tried to overlay a transparent view on your activity and cut out holes to see few stuffs.
here i found an useful example which shows how can you cut out bitmaps and combine them. i would suggest for your problem just take the part of cutting the bitmap and remember to set the imageview backgroung with opacity as shown here
android:background="#00ffffff"
here is the layout i created
<ImageButton
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="#android:color/transparent"
android:src="#drawable/ic_launcher"
android:layout_alignParentRight="true"
android:layout_alignParentBottom="true"/>"
<ImageView
android:id="#+id/img"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#00ffffff"
android:scaleType="centerCrop" >
</ImageView>
</RelativeLayout>
and this is my maniactivity
public class MainActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ImageView iv = (ImageView) findViewById(R.id.img);
Bitmap foreground = BitmapFactory.decodeResource(getResources(), R.drawable.android_cat_wanted);
foreground = punchAHoleInABitmap(foreground);
iv.setImageBitmap(foreground);
}
private Bitmap punchAHoleInABitmap(Bitmap foreground) {
Bitmap bitmap = Bitmap.createBitmap(foreground.getWidth(), foreground.getHeight(), Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(bitmap);
Paint paint = new Paint();
canvas.drawBitmap(foreground, 0, 0, paint);
paint.setAntiAlias(true);
paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
float radius = (float)(getScreenSize().x *.35);
float x = (float) ((getScreenSize().x*.5));
float y = (float) ((getScreenSize().y*.5));
canvas.drawCircle(x, y, radius, paint);
return bitmap;
}
#SuppressLint("NewApi")
private Point getScreenSize() {
WindowManager window = (WindowManager) getSystemService(Context.WINDOW_SERVICE);
Display display = window.getDefaultDisplay();
Point size = new Point();
display.getSize(size);
return size;
}
}
hope you find it useful
Related
I would like to add TextView and EditView into my custom LinearLayout programmatically.
But I don't know how.
Something like this (that doesn't work):
<com.custom.FavoritesViewer
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:visibility="gone"
android:id="#+id/favoritesViewer">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Hello"/>
</com.custom.FavoritesViewer>
and my custom layout
public class FavoritesViewer extends LinearLayout {
private Bitmap fullImage;
private int canvasWidth;
private int canvasHeight;
private final Paint paint = new Paint();
public FavoritesViewer(Context context, AttributeSet attrs) {
super(context, attrs);
setWillNotDraw(false);
initializeCanvasSize(context);
}
private void initializeCanvasSize(Context context) {
final Pair<Integer, Integer> screenSize = Utils.getScreenSize(context);
canvasWidth = screenSize.first;
canvasHeight = screenSize.second;
}
#Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
setMeasuredDimension(canvasWidth, canvasHeight / 3);
}
#Override
protected void onDraw(Canvas cvs) {
if (fullImage == null) {
fullImage = Bitmap.createBitmap(canvasWidth, canvasHeight / 3, Bitmap.Config.ARGB_8888);
final Canvas canvas = new Canvas(fullImage);
paint.reset();
paint.setColor(Color.parseColor("#AA000000"));
canvas.drawRect(0, 0, canvasWidth, canvasHeight / 3, paint);
}
cvs.drawBitmap(fullImage, 0, 0, null);
}
}
So I have a canvas (like background) and I would like to add some standart Views on top. I cannot add it on onDraw.
Is it any way to add View into custom Layout?
EDITTED
I need to implement some special UI with buttons. I want to wrap this in one component. I draw that UI on canvas and somehow should add buttons (It's enough for me to add simple ImageButton, not to draw an image and emulate button's behaviour). That's why I selected Layout as container and need to add Views programmatically.
As long as you call through to super (probably super.onDraw()), I imagine the parent class will draw the views you add as expected. It looks like you're just overriding onDraw, which would prevent the parent LinearLayout class from rendering it's content (like the TextView).
Try commenting out your onDraw method first, and see if the LinearLayout behaves as expected.
Also, what's the goal of the Custom Layout? There may be a better way to achieve your goal.
For a custom AdapterView implementation I'd like to add a color overlay to selected items. How do I add a color overlay to a child of my AdapterView?
If you are using your own layout simply change the container to RelativeLayout (or a Layout class that inherits from RelativeLayout), and put the color overlay after the main layout. All you need is to add a View and set it's background and alpha. alpha set to the value 1 will activate this overlay, whereas setting alpha to 0 will go back to normal.
Example:
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<!-- add your views here -->
<View
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#8000FF00" />
</RelativeLayout>
This will overlay a green layer with 50% alpha over the other views which are before it in the layout.
OK, I did some more research. That's what I finally came up with:
// prepare a gray filter setting saturation to 0, or ...
ColorMatrix cm = new ColorMatrix();
cm.setSaturation(0);
Paint paint = new Paint();
ColorFilter filter = new ColorMatrixColorFilter(cm);
// ... prepare a color filter
ColorFilter filter = new PorterDuffColorFilter(Color.rgb(34, 136, 201), PorterDuff.Mode.OVERLAY);
// create paint
paint.setColorFilter(filter);
// override dispatchDraw of the view
#Override
protected void dispatchDraw(Canvas canvas) {
if (isPressed()) {
canvas.saveLayer(null, paint, Canvas.ALL_SAVE_FLAG);
super.dispatchDraw(canvas);
canvas.restore();
} else {
super.dispatchDraw(canvas);
}
}
I'm writing a custom view that displays signals. In order to shorten my onDraw() time I cache everything I've drawn so far in a Bitmap and just append to that in every onDraw() call. By doing this I can save huge amounts of time since I only need to draw a few fixels at a time instead of redoing the whole thing.
There is on thing bothering me though - it appears as drawing directly to the provided canvas provides a more "accurate" drawing than drawing on the bitmap first and then drawing the bitmap on the canvas. By looking at the lower part of the following picture you can see the difference:
I uploaded a demo project displaying the discrepancy at https://github.com/gardarh/android-uglybitmapdrawing/ but the relevant code is as follows:
#Override
public void onDraw(Canvas canvas) {
if(cachedBitmap == null) {
cachedBitmap = Bitmap.createBitmap(getWidth(), 200, Config.ARGB_8888);
cachedCanvas = new Canvas(cachedBitmap);
}
for(int i = 0; i < COORDS.length; i++) {
float[] curCoords = COORDS[i];
canvas.drawLine(curCoords[0], curCoords[1], curCoords[2], curCoords[3], linePaint);
cachedCanvas.drawLine(curCoords[0], curCoords[1], curCoords[2], curCoords[3], linePaint);
}
canvas.drawBitmap(cachedBitmap, 0, 120, null);
}
Why are the two traces not the same and more importantly, how can I make the lower trace look like the upper one?
The reason for the differences is that the canvas drawing is done by hardware acceleration (GPU), and the bitmap drawing is done by software (CPU). If you disable hardware acceleration, they become the exact same.
If you multiply the X coordinates by 10, you will see that the difference is in the way lines are joined. These are minor one pixel difference and I wouldn't bother with them. I am not sure which one is the more accurate, they seem like just slightly different implementations.
Android framework API provides 2D drawing APIs for simple animation that does not require major dynamic changes.
There are two ways of implementation using these API.
1. Drawing to a View
2. Drawing on a Canvas
1.Drawing a circle to View
Drawing to view is a better option when your UI does not require dynamic changes in the application.
This can be achieved simply by extending the View class and define an onDraw() callback method.
Use the Canvas given to you for all your drawing,
using various Canvas.draw...() methods (Ex: canvas.drawCircle(x / 2, y / 2, radius, paint);). onDraw() is a callback method invoked when the view is initially drawn.
Below is a simple example code to draw a circle:-
MainActivity.java
public class MainActivity extends Activity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(new MyView(this));
}
public class MyView extends View {
public MyView(Context context) {
super(context);
// TODO Auto-generated constructor stub
}
#Override
protected void onDraw(Canvas canvas) {
// TODO Auto-generated method stub
super.onDraw(canvas);
int x = getWidth();
int y = getHeight();
int radius;
radius = 100;
Paint paint = new Paint();
paint.setStyle(Paint.Style.FILL);
paint.setColor(Color.WHITE);
canvas.drawPaint(paint);
// Use Color.parseColor to define HTML colors
paint.setColor(Color.parseColor("#FB9J2F"));
canvas.drawCircle(x / 2, y / 2, radius, paint);
}
} }
2. Drawing rectangle on a canvas
To draw dynamic 2D graphics where in your application needs to regularly re draw itself, drawing on a canvas is a better option. A Canvas works for you as an interface, to the actual surface upon which your graphics will be drawn.
If you need to create a new Canvas, then you must define the bitmap upon which drawing will actually be performed. The Bitmap is always required for a Canvas.
The below example explains to draw a rectangle:-
activity_main.xml
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/mylayout"> </LinearLayout>
MainActivity.java
public class MainActivity extends Activity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Paint paint = new Paint();
paint.setColor(Color.parseColor("#DD4N5C"));
Bitmap bitmap = Bitmap.createBitmap(512, 800, Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(bitmap);
canvas.drawRect(150, 150, 250, 250, paint);
LinearLayout layout = (LinearLayout) findViewById(R.id.mylayout);
layout.setBackgroundDrawable(new BitmapDrawable(bitmap));
}
}
I disagree that you are saving much by going the bitmap route. You might consider a data structure that stores the drawn signal and converting this to a JSON object that can be serialized/deserialized.
As for your question, this is an educated guess but it has more to do with rescaling of the drawn signal, since you are not using getHeight() when you create the bitmap.
i try to draw vertical lines in android.
DrawView drawView;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
drawView = new DrawView(this);
setContentView(drawView);
}
public class DrawView extends View {
Paint paint = new Paint();
public DrawView(Context context) {
super(context);
paint.setColor(Color.RED);
}
#Override
public void onDraw(Canvas canvas) {
canvas.drawLine(0, 100, 0, 0, paint);
}
}
What this draw just one line. What i want to do draw this lines in whole screen. How can i do that? It must draw everywhere in screen vertically. It now draws vertically but just one.
So far from your desired use case, I don't see any reason for you to use a custom view for this. You can set a custom background with repeat enabled:
res/drawable/MyBackground.xml
<?xml version="1.0" encoding="utf-8"?>
<bitmap xmlns:android="http://schemas.android.com/apk/res/android"
android:src="#drawable/lines_image"
android:tileMode="repeat" />
Then for your view, set the background:
res/layout/whatever.xml
<View
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#drawable/MyBackground" />
OR
myView.setBackgroundResource(R.drawable.MyBackground);
lines_image.png should be a 20px (or however much space between you want) wide image with your red line on the right.
It's an important concept for UI development. Don't do complicated things in code when a simple image solution will suffice.
If you absolutely **MUST** Do this in code, Then you just do the drawing in a loop for the width of the canvas.
private static final int LINE_SPACING = 20;
#Override
public void onDraw(Canvas canvas) {
for (int x = 0; x < canvas.getWidth(); x += LINE_SPACING) {
canvas.drawLine(x, 0, x, canvas.getHeight(), paint);
}
}
I want to set a background color to the surface view to my camera surface view.
I am using this for implementing the same. But this example is not complete. Can anyone please help me with some other useful link.
Thanks
There's a workaround to do this.
add a parent viewgroup for the surfaceview, set the background color to this viewgroup instead of the surfaceview;
<FrameLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#android:color/holo_blue_dark">
<com.example.surfacetest.MySurface
android:id="#+id/surface"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</FrameLayout>
add the following for the SurfaceView instance;
surfaceView.setZOrderOnTop(true);
surfaceView.getHolder().setFormat(PixelFormat.TRANSLUCENT);
Now you get the background color you want and the surfaceview is tanslucent.
use surfaceview_obj.setBackgroundColor (int color) to set background color..
to set white color as background use this code
surfaceview_obj.setBackgroundColor(0Xffffffff);
check this
just draw a Rect object with canvas.drawRect(). set the co ordinates to 0,0,screenX,screenY
you have to do a little hack-around to make any background work in SurfaceView, like this:
override the setBackground and setBackgroundDrawable methods
Drawable background
#Override
public void setBackgroundDrawable(Drawable background) {
this.background = background;
}
#Override
public void setBackground(Drawable background) {
this.background = background;
}
don't forget to call setBounds on the drawable
#Override
protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
super.onLayout(changed, left, top, right, bottom);
matrix = null;
if (background != null)
background.setBounds(left, top, right, bottom);
}
then on the code you're locking, drawing, unlocking and posting the canvas you add the background
Canvas c = holder.lockCanvas();
if (background != null)
background.draw(c);
// do your stuff here
holder.unlockCanvasAndPost(c);
works for both XML and Java backgrounds.
Use this
surfaceview.getHolder().setFormat(PixelFormat.TRANSLUCENT);
Just put ARGB value in your draw method before your drawing(e.g. rect, circle etc). I have set it white. The last parameter is transparency.
c.drawARGB(255, 255, 255, 255);