android 音视频学习之路任务一

题目：在 Android 平台绘制一张图片，使用至少 3 种不同的 API，ImageView，SurfaceView，自定义 View

这儿只记录下用SurfaceView绘制图片的过程

自定义MySurfaceView

public class MySurfaceView extends SurfaceView  implements SurfaceHolder.Callback,Runnable{

private SurfaceHolder mHolder;
//用于绘图的canvs
private Canvas canvas;
//子线程标志位
private boolean isDrawing;

//画笔
private Paint paint;
//原图
private Bitmap bitmap;
//指定显示的宽
private int w;
//指定显示的高
private int h;


private void init(){
    mHolder = getHolder();
    mHolder.addCallback(this);
//        setFocusable(true);
//        setFocusableInTouchMode(true);
//        this.setKeepScreenOn(true);
    paint = new Paint();
}
public MySurfaceView(Context context) {
    super(context);
    init();
}
public MySurfaceView (Context context, AttributeSet attrs) {
    super(context, attrs);
    init();
}

public MySurfaceView (Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    init();
}

/**
 * 绘制时，充分利用 SurfaceView 的三个回调方法，
 * 在 surfaceCreated() 方法里开启子线程进行绘制，而子线程使用一个 while (mIsDrawing) {} 的循环来不停地进行绘制，
 * 而在绘制的具体逻辑中，通过 lockCanvas() 方法来获取 Canvas 对象来绘制，
 * 并通过 unlockCanvasAndPost(mCanvas) 方法对画布内容进行提交。
 */

@Override
public void surfaceCreated(SurfaceHolder holder) {
    isDrawing = true;
    new Thread(this).run();
}

@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {

}

@Override
public void surfaceDestroyed(SurfaceHolder holder) {
    isDrawing = false;
}

@Override
public void run() {
    draw();
}

private void draw() {
    try {
        canvas = mHolder.lockCanvas();
        if (bitmap!=null){
            Matrix matrix = new Matrix();
            float scaleWidth = ((float) w)/bitmap.getWidth();
            float scaleHeight = ((float) h)/bitmap.getHeight();
            matrix.postScale(scaleWidth,scaleHeight);
            Bitmap newBitMap = Bitmap.createBitmap(bitmap,0,0,bitmap.getWidth(), bitmap.getHeight(),matrix,true);
            canvas.drawBitmap(newBitMap,0,0,paint);
        }
    }catch (Exception e){
    }finally {
        if (null != canvas){
            /**
             * 将 mHolder.unlockCanvasAndPost(mCanvas);方法放到 finally 代码块中，保证每次都能将内容提交。
             */
            mHolder.unlockCanvasAndPost(canvas);
        }
    }
}

public void setBitmap(Bitmap img,int x,int y){
    if (img!=null){
        bitmap = img;
        w = x;
        h = y;
    }
}
}

MainActivity中的内容

mSv = findViewById(R.id.sv);
final Bitmap bitmap = BitmapFactory.decodeResource(getResources(),R.drawable.img1);
mSv.setBitmap(bitmap,1080,488);

结果

image.png