Implementation principle introduction: The CircleImageView framework in the Java library
Implementation principle introduction: CircleImageView framework in the Java library
CircleImageView is a framework used in the Java library to display round pictures.In many applications, we often need to display round avatars or circular pictures, not traditional rectangular pictures.The CircleImageView framework allows developers to easily convert ordinary pictures into round pictures and display them on the interface.Let's introduce the implementation principles of the CircleImageView framework.
The principle of implementation is as follows:
1. Inherit the ImageView class: The CircleImageView class needs to inherit from the ImageView class in order to use all the properties and methods of the ImageView control.
2. Rewilling the ONDRAW method: In the CircleImageView class, we need to rewrite the ONDRAW method to achieve the circular effect by drawing a round path cut picture.Specific steps are as follows:
3. Get picture resources: In the ONDRAW method, you need to get the picture resources you want to display first.
4. Create Bitmap object: Create a Bitmap object according to the obtained picture resources.
5. Create canvas and brushes: Create canvas and brushes through Bitmap objects, and set the brush to anti -aliasing mode.
6. Calculate the center and radius: According to the width and height of the control, calculate the length of the coordinates and radius of the round heart so that the picture can be drawn in the correct position.
7. Draw a circular path: Use a brush to draw a circular path and use the path as a tailor -made area.
8. Draw a picture: Draw the obtained Bitmap object in the tailoring area, and only retain the part of the circular path range.
9. Complete drawing: Finally, call the parent -class ONDRAW method to complete the drawing.
Java code example:
public class CircleImageView extends ImageView {
public CircleImageView(Context context) {
super(context);
}
public CircleImageView(Context context, AttributeSet attrs) {
super(context, attrs);
}
public CircleImageView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
@Override
protected void onDraw(Canvas canvas) {
Drawable drawable = getDrawable();
if (drawable == null) {
return;
}
if (getWidth() == 0 || getHeight() == 0) {
return;
}
Bitmap b = ((BitmapDrawable) drawable).getBitmap();
Bitmap bitmap = b.copy(Bitmap.Config.ARGB_8888, true);
int w = getWidth();
@SuppressLint("DrawAllocation") Bitmap roundBitmap = getCroppedBitmap(bitmap, w);
canvas.drawBitmap(roundBitmap, 0, 0, null);
}
private Bitmap getCroppedBitmap(Bitmap bmp, int radius) {
Bitmap sbmp;
if (bmp.getWidth() != radius || bmp.getHeight() != radius) {
float smallest = Math.min(bmp.getWidth(), bmp.getHeight());
float factor = smallest / radius;
sbmp = Bitmap.createScaledBitmap(bmp, (int)(bmp.getWidth() / factor), (int)(bmp.getHeight() / factor), false);
} else {
sbmp = bmp;
}
Bitmap output = Bitmap.createBitmap(radius, radius, Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(output);
final int color = 0xff424242;
final Paint paint = new Paint();
final Rect rect = new Rect(0, 0, radius, radius);
paint.setAntiAlias(true);
paint.setFilterBitmap(true);
paint.setDither(true);
canvas.drawARGB(0, 0, 0, 0);
paint.setColor(color);
canvas.drawCircle(radius / 2 + 0.7f, radius / 2 + 0.7f,
radius / 2 + 0.1f, paint);
paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
canvas.drawBitmap(sbmp, rect, rect, paint);
return output;
}
}
The above is the introduction and example code of the implementation principle of the CircleImageView framework.By using the CircleImageView framework, developers can easily display circular pictures in the application to provide users with a more beautiful and unique user interface experience.
