剪切图动画 ClipBitmapMovie

最新推荐文章于 2022-07-28 09:00:00 发布

转载最新推荐文章于 2022-07-28 09:00:00 发布 · 1k 阅读

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#thread #exception #callback #class #null

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本文深入解析了Android中使用Canvas绘制位图的方法，并详细说明了如何通过改变坐标系来实现动画效果，尤其是对mCurrentFrame变量的理解及应用。

public class ClipBitmapMovie extends Activity{

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		// TODO Auto-generated method stub
		super.onCreate(savedInstanceState);
		this.getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
		requestWindowFeature(Window.FEATURE_NO_TITLE);
		setContentView(new ClipBitmapMovieView(this));
	}
}

class ClipBitmapMovieView extends SurfaceView implements Callback,Runnable{
	private SurfaceHolder mSurfaceHolder;
	private Thread mThread;
	private Canvas mCanvas;
	private Paint mPaint;
	private Bitmap mBitmap;
	private int mCurrentFrame;
	private boolean mFlag;

	public ClipBitmapMovieView(Context context) {
		super(context);
		mSurfaceHolder=this.getHolder();
		mSurfaceHolder.addCallback(this);
		mPaint=new Paint();
		mPaint.setColor(Color.WHITE);
		mPaint.setAntiAlias(true);
		
	}

	@Override
	public void surfaceChanged(SurfaceHolder holder, int format, int width,
			int height) {
		// TODO Auto-generated method stub
		
	}

	@Override
	public void surfaceCreated(SurfaceHolder holder) {
		mFlag=true;
		mBitmap=BitmapFactory.decodeResource(getResources(), R.drawable.fish);
		mThread=new Thread(this,"My Thread");
		mThread.start();
			
	}

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

	@Override
	public void run() {
		while (mFlag) {
			long start=System.currentTimeMillis();
			myDraw();
			logic();
			long end=System.currentTimeMillis();
			if(((end-start)<50)){
				try {
					Thread.sleep(50-(end-start));
				} catch (InterruptedException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
		}
	}

	private void logic() {
		mCurrentFrame++;
		if(mCurrentFrame>=10){
			mCurrentFrame=0;
		}
	}

	private void myDraw() {
		try {
			mCanvas=mSurfaceHolder.lockCanvas();
			if (mCanvas != null) {
				mCanvas.drawColor(Color.WHITE);
				mCanvas.clipRect(0, 0, mBitmap.getWidth()/10, mBitmap.getHeight());
				mCanvas.drawBitmap(mBitmap, -mCurrentFrame*mBitmap.getWidth()/10, 0, mPaint);
			}
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}finally{
			if (mCanvas != null) {
				mSurfaceHolder.unlockCanvasAndPost(mCanvas);
			}
		}
	}
	
}

问题一：

mCanvas.drawBitmap(mBitmap, -mCurrentFrame*mBitmap.getWidth()/10, 0, mPaint);

刚开始对这个如何画出图片的参数不理解，通过跟踪调试发现当mCurrentFrame=1时，x和y位置参数是-1200/10,0，也就是说画图的坐标原点在x轴的负半轴上，而且mCurrentFrame越大离原点越远，画的时候是画的整幅图片但是因为clipPath()只截取了一帧的大小所以我们看到的只是一个。

所欲可以理解为从坐标原点开始不断将图片网x轴负半轴拉直到图片完全在x轴负半轴，然后重复这个操作。