Develop Reference

Add View programmatically and after adding on button click change view background

Add View dynamically in LinearLayout and after adding View change any View background on the click button.
LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(width, height);
ImageView img1 = new ImageView(this);
img1.setLayoutParams(layoutParams);
img1.setImageBitmap(icon);
llLayout.addView(img1);
ImageView img2 = new ImageView(this);
img2.setLayoutParams(layoutParams);
img2.setImageBitmap(icon);
llLayout.addView(img2);
ImageView img3 = new ImageView(this);
img3.setLayoutParams(layoutParams);
img3.setImageBitmap(icon);
llLayout.addView(img3);
On button, click change all imageview background or particular ImageView.
Note : llLayout is my linear layout this layout adding in XML

when you are adding imageView into linear layout, at that time you are setImageBitmap to imageView.
if you want to reset Image to Imageview, you should use img1.setImageResource
btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
//use anyone as your requirement
img1.setBackgroundResource(); // for set background resource from drawable folder(for src)
img1.setBackground();// for set background(Drawable)(for background)
img1.setBackgroundColor(); //for set background color(for background)
}
});

I am not sure if I understand the question correctly, but If you mean change specific image background with onClick event on a button .. If you have the image reference change it .. but if you mean you are adding the image view dynamically like inside for loop and you don't have the reference you can create Arraylist and add the added images into it then loop on this arraylist to change all the images background or filter the specific image you want to change

Android: How to add a layer on top no matter how many activities started?

I want to play a gif animation and this view will move on the screen every second, but if I start an activity I need to add this view again and the position will change.
See the attached image below. I need to stick this over every view. Any way to do it?

Create one BaseActivity for all activities in your app to show Overlay View or Layout.
you can inherit BaseActivity on other Activity
You can add gif supported views or layouts
for example i added overlay_layout in my showOverlay method.
you can call showOverlay method where ever you want to show and you can remove with removeOverlay with conditions.
Please note that showOverlay and removeOverlay should be in BaseActivity
void showOverlay(){
LayoutInflater inflater = activity.getLayoutInflater();
layout = inflater.inflate(R.layout.overlay_layout, null);
WindowManager.LayoutParams params = new WindowManager.LayoutParams();
params.gravity = Gravity.BOTTOM;
params.height = WindowManager.LayoutParams.WRAP_CONTENT;
params.width = WindowManager.LayoutParams.WRAP_CONTENT;
params.type = WindowManager.LayoutParams.TYPE_APPLICATION;
final WindowManager mWindowManager = (WindowManager);
activity.getApplicationContext().getSystemService(Context.WINDOW_SERVICE);
mWindowManager.addView(layout, params);
}
void removeOverlay(){
windowManager.removeView(view);
}

set this view into WindowManager and it will always show on top

How do I call a custom class in an Activity?

So I have this DrawAnim.java class file and I want to use its content inside my MainAcitivty. I tried creating an object like this:
DrawAnim draw;
And in onCreate method, I did this:
draw.onDraw(); <- I know I have to pass a parameter but don't know what to pass on.
Here's my class:
public class DrawAnim extends View {
Bitmap ball;
int x, y;
public DrawAnim(Context context) {
super(context);
ball = BitmapFactory.decodeResource(getResources(), R.drawable.globe);
x=0;
y=0;
}
public void onDraw(Canvas canvas){
super.onDraw(canvas);
Rect ourRect = new Rect();
ourRect.set(0,0,canvas.getWidth(),canvas.getHeight()/2);
Paint red = new Paint();
red.setColor(Color.RED);
red.setStyle(Paint.Style.FILL);
canvas.drawRect(ourRect,red);
if( x < canvas.getWidth()) {
x += 10;
} else{
x =0;
}
if( y < canvas.getHeight()){
y+=10;
}else{
y =0;
}
Paint p = new Paint();
canvas.drawBitmap(ball,x,y,p);
invalidate();
}
}

You've extended a View, so you must use it like any other view, either by adding it programmatically at runtime or using it in a layout.

Here is how to add a view in the code. The following steps should be added to the onCreate method of the splash activity.
Get the Layout where the view will be added to in the code, something like LinearLayout linearLayout = findViewById(R.id.linearlayout); (It of course has to be change to your layout and layout-id)
Create an instance of the DrawAnim
Add it to the layout by linearLayout.addView(drawAnim);
Hope this gives an idea and helps.
Here is a link to an animated splashscreen and a link to a very simple splashscreen just to show some alternatives to adding a view. Although the 2nd one is very limited it has a bit animation and does not delay the start of your app.

You should add it like any other views, pass context to your custom view constructor, set Layout params and add it to the parent view group.
DrawAnim draw = new DrawAnim(this); // 'this' as a context in activity
draw.setLayoutParams(layoutParams);
parentViewGroup.addView(draw);

How to add an ImageView over a Button

I want to add an ImageView within the onClick() of the Button. But the ImageView should be aligned to the centre of the button.
How can I do this pragmatically?
I'm creating a new instance of the ImageView to be added on top of the View that called it and it's position is equivalent of the View that called it.
How can I get the X and Y coordinates?
EDIT:
#Override
public void onClick(final View v) {
if(v.getWidth() > v.getHeight()) size = v.getHeight();
if(v.getWidth() < v.getHeight()) size = v.getWidth();
RelativeLayout.LayoutParams button = new RelativeLayout.LayoutParams(size,size);
buttonc = new ImageView(getApplicationContext());
buttonc.setBackgroundResource(R.drawable.round);
layout.addView(buttonc,button);
I'm using the above code to attempt to pragmatically set the size of the ImageView to that of the button, and it's working.
As for the coordinates, I still haven't figured it out.
To add clarity: I'm attempting to create a rounded ripple effect over the view that calls it.

I suggest a better solution create an image view before hand place it in the xml as you see fit,at first set its visibility to false .
On click switch its visibilty to true, and the image will appear
This solution is easier than what you are searching.
Feel free to ask questions

to add Imageview
#Override
public void onClick(final View v) {
//LinearLayout
LinearLayout linearLayout= new LinearLayout(this);
linearLayout.setOrientation(LinearLayout.VERTICAL);
linearLayout.setLayoutParams(new LayoutParams(
LayoutParams.MATCH_PARENT,
LayoutParams.MATCH_PARENT));
//ImageView
ImageView imageView = new ImageView(this);
//image resource
imageView.setImageResource(R.drawable.specs);
//image position
imageView.setLayoutParams(new LayoutParams(
LayoutParams.MATCH_PARENT,
LayoutParams.WRAP_CONTENT));
//adding view to layout
linearLayout.addView(imageView);
//make visible to program
setContentView(linearLayout);
}

How to place buttons below my custom view, so user can opt to save what he/she painted?

First of all, thanks in advance for any help you can provide. This has been driving me nuts and google's been no friend of mine for this.
I've created a DrawView so the user can paint something in the app. What I'd like to do is place that DrawView within a layout XML file, so I can place a TextView title on the top and two buttons on the bottom, one of which will save what the user painted as an image file. So far, all I've been able to do is create an area for the user to paint in. Is there any way to place this DrawView view into an XML file? If not, what alternative solutions do I have?
Also, this is an optional question as I'm sure I'll find the solution by googling, at some point, but is there a better way to smoothly draw along the user's finger movement, other than the canvas.drawLine() method I am currently using?
public class Draw extends Activity {
DrawView drawView;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Set full screen view
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
WindowManager.LayoutParams.FLAG_FULLSCREEN);
requestWindowFeature(Window.FEATURE_NO_TITLE);
drawView = new DrawView(this);
setContentView(drawView);
drawView.requestFocus();
}
}
public class DrawView extends View implements OnTouchListener {
private static final String TAG = "DrawView";
ArrayList <Float> nikpointx = new ArrayList<Float>();
ArrayList <Float> nikpointy = new ArrayList<Float>();
Bitmap nikbmp;
Paint paint = new Paint();
public DrawView(Context context) {
super(context);
setFocusable(true);
setFocusableInTouchMode(true);
this.setOnTouchListener(this);
paint.setColor(Color.WHITE);
paint.setAntiAlias(true);
paint.setStrokeWidth(4);
}
#Override
public void onDraw(Canvas canvas) {
//I'm doing this, because the drawCircle method places circles at different points
//in the screen, rather than drawing smooth lines. I haven't found a more elegant
//solution yet :-(
canvas.drawLine(nikpointx.get(i-1), nikpointy.get(i-1), nikpointx.get(i), nikpointy.get(i), paint);
canvas.setBitmap(nikbmp);
}
}
public boolean onTouch(View view, MotionEvent event) {
// if(event.getAction() != MotionEvent.ACTION_DOWN)
// return super.onTouchEvent(event);
Point point = new Point();
point.x = event.getX();
point.y = event.getY();
points.add(point);
invalidate();
Log.d(TAG, "point: " + point);
nikpointx.add(event.getX());
nikpointy.add(event.getY());
return true;
}
}

You can place you custom view in the xml layout like this:
<full.package.to.customview.DrawView android:id="#+id/idOfCustom"
//other attributes
/>
You can also add custom attributes to your view to set directly from the xml file.
I don't have any solutions for your second problem.
edit: after a quick search on this site i found this -> Android How to draw a smooth line following your finger