Android:ImageView图片缩放、居中
几个重要知识点:
1、布局文件中android:scaleType="matrix" 设置图片动态缩放
2、matrix.postTranslate(dx,dy); 平移图片 matrix.postScale(sx,sy,p.x,p.y); 缩放图片
3、两点的中点、距离计算方式,限制缩放范围函数,在指定区域内移动图片方法
(以下代码网上很多地方有类似的,仅供参考)
public class Main extends Activity { private static final int NONE = 0; private static final int DRAG = 1; private static final int ZOOM = 2; private int mode = NONE; private float oldDist; private Matrix matrix = new Matrix(); private Matrix savedMatrix = new Matrix(); private PointF start = new PointF(); private PointF mid = new PointF(); ImageView view; Bitmap bitmap; DisplayMetrics dm; float minScaleR=0.1f; //最少缩放比例 static final float MAX_SCALE = 4f; //最大缩放比例 float dist = 1f; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); view = (ImageView) findViewById(R.id.image_view); bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.test); dm = new DisplayMetrics(); getWindowManager().getDefaultDisplay().getMetrics(dm); //获取分辨率 matrix.setScale(minScaleR, minScaleR); //开始先缩小 matrix.postTranslate(120, 120); //图片的位置相对于imageview的左上角往右往下各偏移120个像素 view.setImageMatrix(matrix); view.setOnTouchListener(new OnTouchListener() { @Override public boolean onTouch(View v, MotionEvent event) { ImageView view = (ImageView) v; switch (event.getAction() & MotionEvent.ACTION_MASK) { case MotionEvent.ACTION_DOWN: //单点 Toast.makeText(Main.this, bitmap.getWidth()+"*"+bitmap.getHeight(), Toast.LENGTH_LONG).show(); savedMatrix.set(matrix); start.set(event.getX(), event.getY()); mode = DRAG; break; case MotionEvent.ACTION_UP: //单点弹起 case MotionEvent.ACTION_POINTER_UP: //多点弹起 mode = NONE; break; case MotionEvent.ACTION_POINTER_DOWN: //多点 oldDist = spacing(event); if (oldDist > 10f) { savedMatrix.set(matrix); midPoint(mid, event); mode = ZOOM; } break; case MotionEvent.ACTION_MOVE: //按下且在拖动 if (mode == DRAG) { matrix.set(savedMatrix); matrix.postTranslate(event.getX() - start.x,event.getY() - start.y); //xy方向都可以拖动 //matrix.postTranslate(event.getX() - start.x,0); //只在x轴方向拖动 即左右拖动 上下不动 //matrix.postTranslate(0,event.getY() - start.y); //只在y轴方向拖动 即上下拖动 左右不动 } else if (mode == ZOOM) { float newDist = spacing(event); if (newDist > 10f) { matrix.set(savedMatrix); float scale = newDist / oldDist; matrix.postScale(scale, scale, mid.x, mid.y); } } break; } view.setImageMatrix(matrix); CheckScale(); //限制缩放范围 center(); //居中控制 return true; } //两点的距离 private float spacing(MotionEvent event) { float x = event.getX(0) - event.getX(1); float y = event.getY(0) - event.getY(1); return FloatMath.sqrt(x * x + y * y); } //两点的中点 private void midPoint(PointF point, MotionEvent event) { float x = event.getX(0) + event.getX(1); float y = event.getY(0) + event.getY(1); point.set(x / 2, y / 2); } }); } //限制最大最小缩放比例 protected void CheckScale() { float p[] = new float[9]; matrix.getValues(p); if (mode == ZOOM) { if (p[0] < minScaleR) { matrix.setScale(minScaleR, minScaleR); } if (p[0] > MAX_SCALE) { matrix.set(savedMatrix); } } } //自动居中 左右及上下都居中 protected void center() { center(true,true); } private void center(boolean horizontal, boolean vertical) { Matrix m = new Matrix(); m.set(matrix); RectF rect = new RectF(0, 0, bitmap.getWidth(), bitmap.getHeight()); m.mapRect(rect); float height = rect.height(); float width = rect.width(); float deltaX = 0, deltaY = 0; if (vertical) { //int screenHeight = dm.heightPixels; //手机屏幕分辨率的高度 int screenHeight = 400; if (height < screenHeight) { deltaY = (screenHeight - height)/2 - rect.top; }else if (rect.top > 0) { deltaY = -rect.top; }else if (rect.bottom < screenHeight) { deltaY = view.getHeight() - rect.bottom; } } if (horizontal) { //int screenWidth = dm.widthPixels; //手机屏幕分辨率的宽度 int screenWidth = 400; if (width < screenWidth) { deltaX = (screenWidth - width)/2 - rect.left; }else if (rect.left > 0) { deltaX = -rect.left; }else if (rect.right < screenWidth) { deltaX = screenWidth - rect.right; } } matrix.postTranslate(deltaX, deltaY); } }
<?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" > <ImageView android:layout_width="200dip" android:layout_height="200dip" android:layout_centerHorizontal="true" android:layout_centerVertical="true" android:scaleType="matrix" android:src="@drawable/test" android:id="@+id/image_view"> </ImageView> </RelativeLayout>