android放大镜效果实现

public class ShaderView extends View {

private final Bitmap bitmap;

private final ShapeDrawable drawable;

// 放大镜的半径



private static final int RADIUS = 80;

// 放大倍数



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);

// 圆形的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();

// 这个位置表示的是，画shader的起始位置



matrix.setTranslate(RADIUS - x * FACTOR, RADIUS - y * FACTOR);

drawable.getPaint().getShader().setLocalMatrix(matrix);

// bounds，就是那个圆的外切矩形



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);

}

}

基本原理就是使用ShapeDrawable构造一个圆形的drawable，然后它的paint的shader设置为将要放大的图片，然后就是简单的位置移动问题了。放大镜的半径和放大倍数都可以在代码里面修改，代码都有注释，应该很好理解了。

不过，一个问题如果只有一种解决方法的话，那未免有点令人沮丧，想玩点另类的都不行。

玩程序就得玩出个性，玩出激情。哈哈，废话太多，切回正题。

再来看看放大镜的另外一种实现吧

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public class PathView extends View {

private final Path mPath = new Path();

private final Matrix matrix = new Matrix();

private final Bitmap bitmap;

// 放大镜的半径



private static final int RADIUS = 80;

// 放大倍数



private static final int FACTOR = 2;

private int mCurrentX, mCurrentY;



public PathView(Context context) {

super(context);

mPath.addCircle(RADIUS, RADIUS, RADIUS, Direction.CW);

matrix.setScale(FACTOR, FACTOR);



bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.demo);

}



@Override

public boolean onTouchEvent(MotionEvent event) {

mCurrentX = (int) event.getX();

mCurrentY = (int) event.getY();



invalidate();

return true;

}



@Override

public void onDraw(Canvas canvas) {

super.onDraw(canvas);

// 底图



canvas.drawBitmap(bitmap, 0, 0, null);

// 剪切



canvas.translate(mCurrentX - RADIUS, mCurrentY - RADIUS);

canvas.clipPath(mPath);

// 画放大后的图



canvas.translate(RADIUS - mCurrentX * FACTOR, RADIUS - mCurrentY

* FACTOR);

canvas.drawBitmap(bitmap, matrix, null);

}

}

这里使用的是Path类，将canvas剪切出一块圆形区域，在其上绘制放大的部分。

下面我们用这个工具来查看一套PC配置，让你看得更清楚，工程下载地址http://download.csdn.net/detail/hustpzb/4523274