Develop Reference

Rotate ImageButton onCreate without Animation

Is it possible to rotate an ImageButton using the onCreate() function? Or do you have to use an Animation which starts onCreate()? Because with an Animation i can see a little "flick" on Activity start...

you can use ViewCompat.setRotation(buttonInstance, rotationAngle);. From the documentation
Sets the degrees that the view is rotated around the pivot point.

You can override the onDraw() method using a custom class that extends ImageButton (which I'm sure you have).
#Override
protected void onDraw(#NonNull Canvas canvas) {
super.onDraw(canvas);
// Rotate a Bitmap
final Matrix matrix = new Matrix();
matrix.setRotate(angle, imageCenterX, imageCenterY);
canvas.drawBitmap(bitmap, matrix, null);
/*
* OR
**/
// Rotate the canvas
canvas.save(Canvas.MATRIX_SAVE_FLAG);
canvas.rotate(-angle);
canvas.drawBitmap(bitmap, left, top, null);
canvas.restore();
}
Choose one or the other solution, not both together ;)
EDIT
After some quick reflection, that could also work (not tested):
#Override
protected void onDraw(#NonNull Canvas canvas) {
canvas.rotate(-angle);
super.onDraw(canvas);
}

Canvas Path using offset make to many copies (onDraw running twice)

seems I have a problem to understand how offset works. When I use the code below it create me 5 arrowheads, but why? I create one and the use twice offset. So i thought i get 3 arrow heads.
public class legende extends View {
private Paint paint;
private Path arrowPath;
public legende(Context context) {
super(context);
init();
}
public void init(){
paint = new Paint();
arrowPath = new Path();
}
#Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
int width = 1500;
int height = 5000;
setMeasuredDimension(width, height);
}
#Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
arrowPath.moveTo(420, 300);
arrowPath.lineTo(430, 300);
arrowPath.lineTo(420, 310);
arrowPath.lineTo(410, 300);
arrowPath.close();
canvas.drawPath(arrowPath, paint);
arrowPath.offset(0,200);
canvas.drawPath(arrowPath, paint);
arrowPath.offset(0,380);
canvas.drawPath(arrowPath, paint);
}
}
EDIT
Looks like, the problem is, that onDraw is called twice, but i don't know why.
This is how I use it in my fragment activity:
hScrollView.addView(new legende(getActivity()));
scrollView.addView(hScrollView);
relativeLayout.addView(scrollView);

Looks like you´ve got a non thread safe implementation of the onDraw method.
This guy worked it out by using a thread safe implementation: Custom View not drawing properly
Maybe you should copy the path to a local object inside the onDraw and then alter and paint.

OnClick listener does not work after rotate ImageView?

I am using the below code to rotate an ImageView Control
ImageView Iv = new this.findViewById(id)
RotateAnimation a = new RotateAnimation(0, 60);
a.setFillAfter(true);
a.setFillBefore(false);
a.setDuration(0);
Iv.startAnimation(a);
The problem with the above code is that the ImageView looks rotated, but can't be clicked correctly. The coordinates that trigger the click event are the ones at the area the control had before beeing rotated.
Also I tried another solution,, I tried to write a custom view extends ImageView and rotate the control canvas in onDraw() but this solution did not rotate the control , it rotates the content of the control.
#Override
protected void onDraw(Canvas canvas)
{
canvas.rotate(60, getWidth() / 2, getHeight() / 2);
super.onDraw(canvas);
canvas.save();
canvas.restore();
}
#Override
protected synchronized void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(heightMeasureSpec, widthMeasureSpec);
setMeasuredDimension(getMeasuredHeight(), getMeasuredWidth());
}
any idea how can I rotate the control itself and keep it clickable ?
Thanks in advance,

Animation doesn't change your views position. It's a common issue with animation. Please look here.

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.

How to take canvas on imageview in android

I want to display canvas contents on imageview in android
i am not understanding the
imageview.draw(canvas);
Heres my code:
public class Matrix extends Activity {
public Bitmap mybitmap,newbmp,bitmap,bmp;
ImageView imageview;
Paint paint;
#Override
public void onCreate(final Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
imageview=(ImageView)findViewById(R.id.ImageView01);
imageview.setDrawingCacheEnabled(true);
}
protected void onDraw(Canvas canvas)
{
imageview.draw(canvas);
mybitmap=BitmapFactory.decodeResource(getResources(), R.drawable.image);
canvas.drawBitmap(mybitmap, 0, 0, paint);
}
}

"I want to display canvas contents on imageview in android"
So you want to draw what is on the Canvas in to your ImageView? If that's what you want then you need to read the links given by johike because you seem to have become confused a little.
The following in your code:
imageview.draw(canvas);
Does NOT mean draw the contents of canvas in to the imageview. It means the opposite, draw the imageview to the canvas.

Even if your question is not detailed enough to give you a precise answer I can give you the following hints:
Derive your on class from ImageView and then override the onDraw method
#Override
protected void onDraw(Canvas canvas) {
// draw a blue background
canvas.drawColor(Color.BLUE);
// additional drawings here
}
Further study the Android references:
http://developer.android.com/guide/topics/graphics/2d-graphics.html
http://developer.android.com/reference/android/graphics/Canvas.html