Develop Reference

CustomView not showing inside ScrollView

New Android programmer here.
I'm trying to display an .png image as a bitmap on Android. The only way I have been able to display the converted image at all is with a custom class that extends View. However, my image is too large to be displayed entirely on the screen and I would like to be able to scroll with it. But when I define a ScrollView and put the Canvas with the Bitmap into it, I get a blank screen. I had no luck setting this up with the layout file, so it is all done in the Activity class.
This is where the Activity is created:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
ScrollView scroll = new ScrollView(this);
scroll.addView(new CustomView(this));
setContentView(scroll);
}
And this is my CustomView class:
private class CustomView extends View{
public CustomView(Context context) {
super(context);
}
#Override
protected void onDraw(Canvas canvas){
Bitmap bitmapMap = BitmapFactory.decodeResource(getResources(),R.drawable.resourceimage);
canvas.drawBitmap(bitmapMap,0,0,null);
this.setWillNotDraw(false);
}
}
And if I replace this line of code in my Activity: setContentView(scroll)
with this line: setContentView(new CustomView(this)), I can see the image, albeit not the entire image. So, is there a way to set this up in the layout files instead? Or is there something I'm missing that I need to declare in the ScrollView class?
EDIT: I would prefer not to use ImageView, because I would like to change the image in specific locations, and using bitmap seemed to be the easiest way to accomplish that, via x and y coordinates.

Your custom view needs to override the onMeasure method and properly set the measured width and height so that the parent views (in this case the ScrollView) can know how much space to allocate for the child.

How to connect button actions with surfaceview canvas drawables?

My problem is that I don't know how to change position of a canvas drawable on click of
my button that it's located in the main activity and not to surfaceview so the code to work should be on surfaceview here is what I've got
public class JumpOnClick extends Activity implements OnClickListener{
DrawingSurface ds;
FrameLayout frm;
Button btnC;
int color=0xfff00000;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
ds=new DrawingSurface(this);
setContentView(R.layout.activity_jump_on_click);
frm=(FrameLayout)findViewById(R.id.frameLayout);
frm.addView(ds);
btnC=(Button)findViewById(R.id.buttonColor);
btnC.setOnClickListener(this);
}
#Override
public void onClick(View v) {
// how to connect actions in here for my sprites on my surfaceview
// for example AnimatedSprite a = new AnimatedSprite();
// if(b == null)
//b=BitmapFactory.decodeStream(res.openRawResource(R.drawable.explosion));
// a.Initialize(b, 120, 159, 7, 20, true);
// mSprites.add(a);
}
}

if I understand correctly,
define two static float variables in your surfaceview class respectively x and y, and when you do your drawing in your surfaceview just use this variables as position parameters in your surfaceview's draw method. And then back in your activity in your onClick method of the button just change these x,y variables, as you can access them without any need to create object.

I believe that you need to add layout rules to your button to place it in the Surfaceview (Actually a button cant be added to a SurfaceView, you need to create an illusion with a Layout in your Activity and place the button to this Layout).
You can check this simple solution at this video https://www.youtube.com/watch?v=8qE9TQjQ5no&t=31s
that is placing buttons to a SurfaceView at the top and bottom using a Relativelayout. My opinion is with that technique you wont need the ontouchevent method neither the x,y position, you will need that if you create a button in the ondraw method (then wont be a button but a bitmap image)...My opinion is to stick with the first solution if the position is the problem so it can act as a button with the onclicklistener.

Getting window size before adding controls

I have a custom view with a public function that adds a control as a child of the view, and I want to call it from my activity. The problem is that I need to know the size of the view in the function in order to place the control. I can't override onMeasure to get the measures because my view inherits from another custom view in which this function is final. I tried overriding measureChildren, but it gets called too late (even after onResume on the activity in which the view is placed in). What can I do in order to have the size before the activity calls the function in the view?

One possibility is to measure your view back in the activity then set properties of the view for it's internal methods to use.
Using a global layout listener has always worked well for me. It has the advantage of being able to remeasure things if the layout is changed, e.g. if something is set to View.GONE or child views are added/removed.
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
// inflate your main layout here (use RelativeLayout or whatever your root ViewGroup type is
LinearLayout mainLayout = (LinearLayout ) this.getLayoutInflater().inflate(R.layout.main, null);
// set a global layout listener which will be called when the layout pass is completed and the view is drawn
mainLayout.getViewTreeObserver().addOnGlobalLayoutListener(
new ViewTreeObserver.OnGlobalLayoutListener() {
public void onGlobalLayout() {
// at this point, the UI is fully displayed
}
}
);
setContentView(mainLayout);
http://developer.android.com/reference/android/view/ViewTreeObserver.OnGlobalLayoutListener.html

If you want the the display dimensions in pixels you can use getSize:
Display display = getWindowManager().getDefaultDisplay();
Point size = new Point();
display.getSize(size);
int width = size.x;
int height = size.y;

How do I position ZoomButtonsController in custom ImageView?

Layouting in Android is getting me rather perplexed.
I'm slowly implementing a custom ImageView where I'd like to make use of the ZoomButtonsController.
However, I would like to decide where the zoom buttons go in the layout and I can't figure out how to move them from the default bottom center position.
I have been experimenting with layouting simple views such as buttons in the main activity and this seems to be working as I would guess and expect.
In the case of the ZoomButtonsController I would however like to reposition them. I'm using a RelativeLayout as the mail layout and add the ZoomButtonsController within the custom ImageView.
The Activity code
public class ImageViewActivity extends Activity {
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
CustomImageView imageView = new CustomImageView(this);
relativeLayout.addView(imageView);
}
}
The CustomImageView code
public class CustomImageView extends ImageView {
private ZoomButtonsController mZoomButtons;
public CustomImageView(Context context) {
super(context);
RelativeLayout.LayoutParams layoutParams = new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.FILL_PARENT, RelativeLayout.LayoutParams.FILL_PARENT);
mZoomButtons = new ZoomButtonsController(this);
mZoomButtons.getZoomControls();
layoutParams.addRule(RelativeLayout.ALIGN_PARENT_TOP);
layoutParams.addRule(RelativeLayout.CENTER_HORIZONTAL);
setLayoutParams(layoutParams);
}
#Override
public boolean onTouchEvent(MotionEvent ev) {
Log.d("TAG", "touch");
mZoomButtons.setVisible(true);
return true;
}
}
I've tested with WRAP_CONTENT in the parameters, but this only makes the zoom buttons disappear.

As a matter of fact, I couldn't position the ZoomButtonsController in any way and in the end had to accept the default placement.

Adding View to Relative Layout behind an existing view causes screen flicker

I'm trying to insert a View behind another view that is taking up the full screen and then later removing the view in the front to reveal the only remaining view. Functionally, everything is working as expected but the problem is that when I call View.addView() to add the second view, specifying to add it at index 0 so it is behind the first view, the screen flickers. It's almost as if the view is actually getting added in front of the first view for a fraction of a second and then it is hidden again as it is moved behind it.
Here's what I'm doing:
When the Activity is created I add an ImageView to a RelativeLayout and make the RelativeLayout instance the Activity's content view:
protected void onCreate(Bundle bundle) {
super.onCreate(bundle);
m_layout = new RelativeLayout(this);
m_layout.setBackgroundColor(Color.BLACK);
m_splashImage = new ImageView(this);
m_splashImage.setImageResource(R.drawable.splash);
m_splashImage.setScaleType(ScaleType.FIT_XY);
m_layout.addView(m_splashImage,
new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.FILL_PARENT,
RelativeLayout.LayoutParams.FILL_PARENT));
setContentView(m_layout);
}
When the Activity is started, I created and add the GLSurfaceView to the RelativeLayout at index 0, so it is behind the ImageView:
protected void onStart() {
super.onStart();
m_layout.addView(new MyGLSurfaceView(), 0,
new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.FILL_PARENT,
RelativeLayout.LayoutParams.FILL_PARENT));
}
Later, after all of the loading is done and the GLSurfaceView is ready to continuously render,
the splash ImageView is removed and cleaned up.
public void hideSplashScreen() {
if (m_splashImage != null) {
m_layout.removeView(m_splashImage);
m_splashImage = null;
}
}
Is there a better way to do this that doesn't require creating the GLSurfaceView before the onStart() is called?

Have you tried using view.setVisibility(View.GONE) on of the view that you adding behind? Of course before you are adding it.