Android自定義控制元件-----放大鏡
阿新 • • 發佈:2019-01-27
public class ShaderView extends View { private final Bitmap bitmap; private final ShapeDrawable drawable; // 放大鏡的半徑 private static final int RADIUS = 80; // 放大倍數 private static final int FACTOR = 3; private final Matrix matrix = new Matrix(); public ShaderView(Context context) { super(context); Bitmap bmp = BitmapFactory.decodeResource(getResources(),R.drawable.demo); bitmap = bmp; BitmapShader shader = new BitmapShader(Bitmap.createScaledBitmap(bmp, bmp.getWidth() * FACTOR, bmp.getHeight() * FACTOR, true), TileMode.CLAMP, TileMode.CLAMP); // 圓形的drawable drawable = new ShapeDrawable(new OvalShape()); drawable.getPaint().setShader(shader); drawable.setBounds(0, 0, RADIUS * 2, RADIUS * 2); } @Override public boolean onTouchEvent(MotionEvent event) { final int x = (int) event.getX(); final int y = (int) event.getY(); // 這個位置表示的是,畫shader的起始位置 matrix.setTranslate(RADIUS - x * FACTOR, RADIUS - y * FACTOR); drawable.getPaint().getShader().setLocalMatrix(matrix); // bounds,就是那個圓的外切矩形 drawable.setBounds(x - RADIUS, y - RADIUS, x + RADIUS, y + RADIUS); invalidate(); return true; } @Override public void onDraw(Canvas canvas) { super.onDraw(canvas); canvas.drawBitmap(bitmap, 0, 0, null); drawable.draw(canvas); } }