一、要求
利用ScaleGestureDetector这个类实现图片缩放。
二、代码
public class MainActivity extends ActionBarActivity { private SurfaceView mSurfaceView = null; private SurfaceHolder mSurfaceHolder = null; private ScaleGestureDetector mScaleGestureDetector = null; private Bitmap mBitmap = null; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); mSurfaceView = (SurfaceView) this.findViewById(R.id.surfaceview); mSurfaceHolder = mSurfaceView.getHolder(); mScaleGestureDetector = new ScaleGestureDetector(this, new ScaleGestureListener()); mSurfaceView.post(new Runnable() { @Override public void run() { mBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.guanmjie); // 锁定整个SurfaceView Canvas mCanvas = mSurfaceHolder.lockCanvas(); // 画图 mCanvas.drawBitmap(mBitmap, 0f, 0f, null); // 绘制完成,提交修改 mSurfaceHolder.unlockCanvasAndPost(mCanvas); // 重新锁一次 mSurfaceHolder.lockCanvas(new Rect(0, 0, 0, 0)); mSurfaceHolder.unlockCanvasAndPost(mCanvas); } }); } @Override public boolean onTouchEvent(MotionEvent event) { // 返回给ScaleGestureDetector来处理 return mScaleGestureDetector.onTouchEvent(event); } public class ScaleGestureListener implements ScaleGestureDetector.OnScaleGestureListener { private float scale; private float preScale = 1;// 默认前一次缩放比例为1 @Override public boolean onScale(ScaleGestureDetector detector) { // TODO Auto-generated method stub Matrix mMatrix = new Matrix(); float previousSpan = detector.getPreviousSpan(); float currentSpan = detector.getCurrentSpan(); if (currentSpan < previousSpan) { // 缩小 // scale = preScale-detector.getScaleFactor()/3; scale = preScale - (previousSpan - currentSpan) / 1000; } else { // 放大 // scale = preScale+detector.getScaleFactor()/3; scale = preScale + (currentSpan - previousSpan) / 1000; } mMatrix.setScale(scale, scale); // 锁定整个SurfaceView Canvas mCanvas = mSurfaceHolder.lockCanvas(); // 清屏 mCanvas.drawColor(Color.BLACK); // 画缩放后的图 mCanvas.drawBitmap(mBitmap, mMatrix, null); // 绘制完成,提交修改 mSurfaceHolder.unlockCanvasAndPost(mCanvas); // 重新锁一次 mSurfaceHolder.lockCanvas(new Rect(0, 0, 0, 0)); mSurfaceHolder.unlockCanvasAndPost(mCanvas); return false; } @Override public boolean onScaleBegin(ScaleGestureDetector detector) { // 一定要返回true才会进入onScale()这个函数 return true; } @Override public void onScaleEnd(ScaleGestureDetector detector) { preScale = scale;//记住本次的缩放后的图片比例 } } }
activity_main.xml如下:
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical" > <SurfaceView android:id="@+id/surfaceview" android:layout_width="fill_parent" android:layout_height="fill_parent" /> </LinearLayout>
总结:本例利用了matrix和canvas,对图片进行缩放;本demo还可以改造,不需matrix和canvas,在获得scale值之后对其他控件等缩放都可以!功能强大!而且简单明了,完全无bug!
下面是一个功能强大的改造的例子:
可以实现以下需求:
1.两个手指进行缩放布局
2.所有子控件也随着缩放,
3.子控件该有的功能不能丢失(像button有可被点击的功能,缩放后不能丢失该功能)
链接:http://www.cnblogs.com/johnsonwei/p/5830277.html
时间: 2024-10-12 08:55:38