Android 实现放大镜功能 需用到Bitmap、BitmapShader、Matrix、Canvas、BitmapFactory等Android的类。
如下是源码：
package com.lulu; import android.app.Activity; import android.content.Context; import android.graphics.Bitmap; import android.graphics.BitmapFactory; import android.graphics.BitmapShader; import android.graphics.Canvas; import android.graphics.Matrix; import android.graphics.Shader.TileMode; import android.graphics.drawable.ShapeDrawable; import android.graphics.drawable.shapes.OvalShape; import android.os.Bundle; import android.view.MotionEvent; import android.view.View; import android.widget.FrameLayout; public class MainActivity extends Activity { @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); FrameLayout ll = (FrameLayout) findViewById(R.id.frameLayout1); // 获取布局文件中的帧布局管理器 ll.addView(new MyView(this)); // 将自定义视图添加到帧布局管理器中 } public class MyView extends View { private Bitmap bitmap; // 源图像，也就是背景图像 private ShapeDrawable drawable; private final int RADIUS = 57; // 放大镜的半径 private final int FACTOR = 2; // 放大倍数 private Matrix matrix = new Matrix(); private Bitmap bitmap_magnifier; // 放大镜位图 private int m_left = 0; // 放大镜的左边距 private int m_top = 0; // 放大镜的顶边距 public MyView(Context context) { super(context); Bitmap bitmap_source = BitmapFactory.decodeResource(getResources(), R.drawable.source); //获取要显示的源图像 bitmap = bitmap_source; BitmapShader shader = new BitmapShader(Bitmap.createScaledBitmap( bitmap_source, bitmap_source.getWidth() * FACTOR, bitmap_source.getHeight() * FACTOR, true), TileMode.CLAMP, TileMode.CLAMP); //创建BitmapShader对象 // 圆形的drawable drawable = new ShapeDrawable(new OvalShape()); drawable.getPaint().setShader(shader); drawable.setBounds(0, 0, RADIUS * 2, RADIUS * 2); // 设置圆的外切矩形 bitmap_magnifier = BitmapFactory.decodeResource(getResources(), R.drawable.magnifier); //获取放大镜图像 m_left = RADIUS - bitmap_magnifier.getWidth() / 2; // 计算放大镜的默认左边距 m_top = RADIUS - bitmap_magnifier.getHeight() / 2; // 计算放大镜的默认右边距 } @Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); canvas.drawBitmap(bitmap, 0, 0, null); // 绘制背景图像 canvas.drawBitmap(bitmap_magnifier, m_left, m_top, null); // 绘制放大镜 drawable.draw(canvas); // 绘制放大后的图像 } @Override public boolean onTouchEvent(MotionEvent event) { final int x = (int) event.getX(); // 获取当前触摸点的X轴坐标 final int y = (int) event.getY(); // 获取当前触摸点的Y轴坐标 matrix.setTranslate(RADIUS - x * FACTOR, RADIUS - y * FACTOR); // 平移到绘制shader的起始位置 drawable.getPaint().getShader().setLocalMatrix(matrix); drawable.setBounds(x - RADIUS, y - RADIUS, x + RADIUS, y + RADIUS); // 设置圆的外切矩形 m_left = x - bitmap_magnifier.getWidth() / 2; // 计算放大镜的左边距 m_top = y - bitmap_magnifier.getHeight() / 2; // 计算放大镜的右边距 invalidate(); // 重绘画布 return true; } } }
