android开发-简单动画2

前面一篇写的是利用postInvalidate函数和onDraw函数来实现简单动画的，这里要说的第二种方法我感觉比较类似，是利用擦除函数来完成这个简单动画的***。简单的说就是先利用和上一篇中一样的Paint（画笔），Canvas（画布）这些类来进行绘画，然后在进行下次绘画之前将前面一次的绘画擦除，在进行新的绘画，在时间很快的情况下就是一个简单的动画了，擦除绘画就是将画布的颜色恢复就行。个人觉得这和前面一种做法差不多。这里还是用画线为例。

[code]public class SlideViewSingleSelfVideoActivity extends SurfaceView implements SurfaceHolder.Callback {

    protected SurfaceHolder surfaceholder;
//  private MyThread thread;
    private static final int SPEEN_DISTANCE = 5; // 中间线每次刷新移动的距离
    private Paint paint; // 画笔对象的引用 
    private int slideTop; // 中间滑动线的最顶端位置 
    private int slideBottom; // 中间滑动线的最底端位置 
    private int slideLeft; // 中间滑动线的最左边位置
    private int slideRight; // 中间滑动线的最右边位置

    public SlideViewSingleSelfVideoActivity(Context context, AttributeSet attrs) {
        super(context, attrs);
        // TODO Auto-generated constructor stub
        surfaceholder = getHolder();  // 获取SurfaceHolder对象 
        surfaceholder.addCallback(this);  // 添加回调
        surfaceholder.setFormat(PixelFormat.TRANSPARENT);  // 设置为透明  
//      setZOrderOnTop(true);  // 设置视图在顶层

    }

    public void clearDraw() {  
        synchronized(surfaceholder) {
            Canvas canvas = surfaceholder.lockCanvas();  
            canvas.drawColor(Color.BLUE);// 清除画布  
            surfaceholder.unlockCanvasAndPost(canvas);  
        }   
    } 

    public void Draw(int y) { 
        synchronized(surfaceholder) {
            Canvas canvas = surfaceholder.lockCanvas();
            canvas.drawColor(Color.BLUE); // 这里是绘制背景
            paint = new Paint();
            paint.setAntiAlias(true); // 反锯齿 
            //获取屏幕的宽高
            int width = canvas.getWidth();  

            slideLeft = 50;
            slideRight = width - slideLeft;
            slideTop = y;
            slideBottom = y + 5;

            //绘制中间的线,每次刷新界面，中间的线往下移动SPEEN_DISTANCE
            paint.setColor(Color.RED); // 将画笔设置成红色
            canvas.drawRect(slideLeft, slideTop, slideRight, slideBottom, paint);
            surfaceholder.unlockCanvasAndPost(canvas);
        }
    }

    @Override
    public void surfaceChanged(SurfaceHolder arg0, int arg1, int arg2, int arg3) {
        // TODO Auto-generated method stub

    }

    @Override
    public void surfaceCreated(SurfaceHolder arg0) {
        // TODO Auto-generated method stub

    }

    @Override
    public void surfaceDestroyed(SurfaceHolder arg0) {
        // TODO Auto-generated method stub

    }

}

然后在主Activity中调用。

[code]    /*
     * 刷新屏幕，移动绘制线
     */
    private SlideViewSingleSelfVideoActivity m_vVideoViewDraw = null;
    private int lastY = 350;
    private TimerTask mMoveTask;

    private void start() {
        m_vVideoViewDraw =(SlideViewSingleSelfVideoActivity)findViewById(SystemView.getViewID(this,"videoview_surface_draw"));
        m_vVideoViewDraw.setVisibility(View.VISIBLE);
        mMoveTask = new TimerTask() {
            @Override
            public void run() {
                m_vVideoViewDraw.Draw(lastY);
                lastY += 20; // 向下
                if(lastY > 1100) {
                    m_vVideoViewDraw.clearDraw();
                    lastY = 350;
                }
            }
        };
        mVideoRecordTimer.schedule(mMoveTask, 0,100);
    }

因为不是demo，所以代码可能不详实。