Android 实现放大镜功能源码

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
}

@Over
4000
ride
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;
}
}

}