Android-Canvas使用技巧

最近项目涉及到多媒体这一块，因此对Canvas的使用技巧做一个总结，供以后查询。下面是一个Bitmap旋转的Demo：

package com.jony.canvas;

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageView;

public class MainActivity extends Activity implements OnClickListener {
    private final static int UPDATE = 0x1;
    private Button rotate;
    private static ImageView image;
    // Handler应该使用static和final关键字进行限制，否则引用该对象的时候可能存在内存泄露
    public static final Handler myHandler = new Handler() {
        public void handleMessage(android.os.Message msg) {
            switch (msg.what) {
                case UPDATE:
                    Bitmap destmap = (Bitmap) msg.obj;
                    image.setImageBitmap(destmap);// 设置ImageView的显示内容
                    break;
                default:
                    break;
            }
        };
    };

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        rotate = (Button) findViewById(R.id.rotate);
        image = (ImageView) findViewById(R.id.image);
        rotate.setOnClickListener(this);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }

    @Override
    public void onClick(View v) {
        final Bitmap bitmap = BitmapFactory.decodeResource(getResources(),
                R.drawable.image01);
        new MyThread(bitmap).start();

    }

    class MyThread extends Thread {
        private final static int ROTATE_DGREES = 45;
        private Bitmap bitmap;
        private Paint paint;
        private Matrix matrix;

        public MyThread(Bitmap bitmap) {
            this.bitmap = bitmap;
            matrix = new Matrix();
        }

        @Override
        public void run() {
            for (int i = 0; i < ROTATE_DGREES; i++) {
                // 创建一个原图大小的空白Bitmap
                Bitmap bg = Bitmap.createBitmap(bitmap.getWidth(),
                        bitmap.getHeight(), Config.ARGB_8888);
                // 创建画布
                Canvas canvas = new Canvas(bg);
                //canvas.drawColor(0xFF000000);清屏处理
                canvas.drawColor(0x00000000);// 设置画布为透明背景
                // 达到图片旋转效果有两种方式：1、旋转Canvas 2、矩阵旋转
                canvas.rotate(i);// 旋转角度
                canvas.drawBitmap(bitmap, 0, 0, paint);
                
                // 旋转矩阵
                //matrix.setRotate(i);
                //canvas.drawBitmap(bitmap, matrix, paint);
                
                // image.setImageBitmap(bg);// 切忌，非UI线程不能处理UI信息
                Message message = myHandler.obtainMessage();
                message.obj = bg;
                message.what = 0x1;
                myHandler.sendMessage(message);
            }
            // 复位
            Message message = myHandler.obtainMessage();
            message.obj = bitmap;
            message.what = 0x1;
            myHandler.sendMessage(message);
        }
    }
}

代码比较简单，在此不做过多解释。
 效果图：

                    

 代码下载地址：

http://download.youkuaiyun.com/download/weihan1314/4730830