I am a newbie to graphics in Android (although I am pretty well-versed with Android programming itself). I am trying to display a "lightbulb" in my app. Based on some values, I would like to change the "brightness" of the lightbulb.
I used a PNG image for this.
<View
android:id="@+id/view2"
android:layout_width="59dp"
android:layout_height="65dp"
android:background="@drawable/lightbulb" />
And, the code is this:
final View normalView = findViewById(R.id.view2);
//Where I need to set the alpha
int alphaValue = /*Some calculation*/
normalView.getBackground().setAlpha(alphaValue);
normalView.invalidate();
The png file is a transparent graphic with only the outline of the bulb in black. Now, what happens is when I set the alpha to a lower value (closer to 0), the entire graphic becomes transparent. I want only the content of the bulb to become transparent. I wish the outline of the bulb to stay visible.
I did try creating my custom View as follows, but now I don't see the graphic at all.
class LightbulbView extends View {
private BitmapDrawable mLightbulbDrawable;
private Paint mPaint;
/*All constructors which call through to super*/
private void initialize(){
mLightbulbDrawable = new BitmapDrawable(getResources(), BitmapFactory.decodeResource(getResources(), R.drawable.lightbulb));
mPaint = new Paint();
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
mLightbulbDrawable.draw(canvas);
}
/*Without this, I get an NPE when I do a getBackground on this view*/
@Override
public Drawable getBackground() {
return mLightbulbDrawable;
//return super.getBackground();
}
}
And, of course, using an ImageView does no good either. The result is exactly the same.
<ImageView
android:layout_width="wrap_content"
android:id="@+id/imageView1"
android:layout_height="wrap_content"
android:src="@drawable/lightbulb"
></ImageView>
And here's the code
final ImageView imageView = (ImageView) findViewById(R.id.imageView1);
imageView.setAlpha(alphaValue);
So, what is the best way to do this in Android?
SOLUTION
This is how I did it. Please see the accepted answer (by @Petrus) for more details:
<FrameLayout
android:id="@+id/frameLayout1"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
>
<ImageView
android:layout_height="wrap_content"
android:src="@drawable/lightbulb_content"
android:layout_width="wrap_content"
android:id="@+id/bulbContent"
></ImageView>
<ImageView
android:layout_height="wrap_content"
android:src="@drawable/lightbulb"
android:layout_width="wrap_content"
android:id="@+id/bulb"
></ImageView>
</FrameLayout>
And in code:
final ImageView bulbContent = (ImageView) findViewById(R.id.bulbContent);
//Where I need to set the alpha
int alphaValue = /*Some calculation*/
normalView.getBackground().setAlpha(alphaValue);
bulbContent.setAlpha(alphaValue);
Here, lightbulb.png is an image with just the outline of the bulb; lightbulb_content.png is an image with the "contents" of the bulb.
