Android SurfaceView简例

冷不防 2023-10-17 15:47 31阅读 0赞

**Android SurfaceView简例**

Android中各的SurfaceView和View有很大的不同，两者应用场景不同。大多数View能做的事情SurfaceView也可以，但是SurfaceView效率更高。Android的View绘制过程由Android系统控制，刷新机制开发者比较难以控制。而SurfaceView支持高频、多线程绘制。SurfaceView不存在是否在Android UI主线程绘制问题。通常SurfaceView用于游戏、多媒体（视频）开发。  
现在给出一个例子。

写一个自定义的SurfaceView，MySurfaceView.java：

package zhangphil.view;
    
    import android.content.Context;
    import android.graphics.Canvas;
    import android.graphics.Color;
    import android.graphics.Paint;
    import android.util.AttributeSet;
    import android.view.SurfaceHolder;
    import android.view.SurfaceView;
    
    /**
     * Created by Phil on 2017/9/12.
     */
    
    public class MySurfaceView extends SurfaceView {
        public MySurfaceView(Context context, AttributeSet attrs) {
            super(context, attrs);
            init();
        }
    
        private void init() {
            SurfaceHolder holder = getHolder();
    
            final MyTask task = new MyTask(holder);
    
            holder.addCallback(new SurfaceHolder.Callback() {
                @Override
                public void surfaceCreated(SurfaceHolder surfaceHolder) {
                    task.startTask();
                }
    
                @Override
                public void surfaceChanged(SurfaceHolder surfaceHolder, int format, int width, int height) {
    
                }
    
                @Override
                public void surfaceDestroyed(SurfaceHolder surfaceHolder) {
                    task.stopTask();
                }
            });
        }
    
        private class MyTask extends Thread {
            private int width;
            private int height;
    
            private SurfaceHolder surfaceHolder;
            private Paint paint;
            private float radius = 0;
    
            public boolean stopTask = false;
    
            public MyTask(SurfaceHolder surfaceHolder) {
                this.surfaceHolder = surfaceHolder;
    
                paint = new Paint();
                paint.setAntiAlias(true);
                paint.setColor(Color.RED);
                paint.setStyle(Paint.Style.STROKE);
                paint.setStrokeWidth(10f);
            }
    
            public void startTask() {
                stopTask = false;
                this.start();
            }
    
            public void stopTask() {
                stopTask = true;
            }
    
            @Override
            public void run() {
                while (!stopTask) {
                    try {
                        Thread.sleep(1);
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
    
                    Canvas canvas = surfaceHolder.lockCanvas();
    
                    width = getWidth();
                    height = getHeight();
    
                    canvas.drawColor(Color.WHITE);
                    canvas.drawCircle(width / 2, height / 2, radius++, paint);
    
                    surfaceHolder.unlockCanvasAndPost(canvas);
    
                    //如果半径大于边界，置0.
                    if (radius >= (width / 2)) {
                        radius = 0;
                    }
                }
            }
        }
    }

测试的activity\_main.xml：

<?xml version="1.0" encoding="utf-8"?>
    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@android:color/holo_blue_light"
        tools:context="zhangphil.view.MainActivity">
    
        <zhangphil.view.MySurfaceView
            android:layout_width="150dp"
            android:layout_height="150dp"
            android:layout_centerInParent="true" />
    </RelativeLayout>

代码运行结果：  
![Center][]

[Center]: https://img-blog.csdn.net/20170913093223403?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvemhhbmdwaGls/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/Center