一行代码实现view拖拽移动、双指缩放效果（最顺滑的缩放）
实现原理：通过重写View.OnTouchListener实现拖拽与缩放效果；
注意：如果对含有子类的viewGroup设置，子类的大小可能不变，因为缩放的效果代码用的是view.layout(),只是改变了当前设置触摸监听view的大小，里面子类的大小是没有变的；
如果想子类一起改变，需要用到View.setScaleX()，View.setScaleY()这两个缩放大小方法去缩放，但是这个方法有个问题，在同一个view的onTouch中如果调这两个方法，缩放会造成频闪问题，原因是第二个触摸点坐标发生了异常变化，所以不能再同一个view中调用，想出来的解决方案就是，在需要缩放的view上覆盖一个触摸层，大小就是触摸操作的范围，对这个触摸层设置触摸监听，目的是得到缩放比，然后在效果view上进行缩放，下面类里面也写了这种方案，找到mEffectView注释去掉就行了；
一行代码对你的view加上触摸效果：
myView.setOnTouchListener(new DragTouchListener());设置属性：关闭拖拽
DragTouchListener dragTouchListener = new DragTouchListener(rlParent);
dragTouchListener.setCancleTouchDrag(false);设置属性：关闭缩放
dragTouchListener.setTouchTwoZoomEnable(false);自定义OnTouchListener：DragTouchListener
import android.util.DisplayMetrics;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.view.ViewTreeObserver;
/**
* 对view实现拖拽移动、双指缩放效果（默认全开启）
* 使用方法：1创建DragTouchListener实例 ；2设置监听 view.setOnTouchListener(DragTouchListener);
* Created by alan on 2019/1/3 0007.
*/
public class DragTouchListener implements View.OnTouchListener {
private DisplayMetrics dm;
private int maxWidth;
private int maxHeight;
private int lastX;
private int lastY;
//刚触摸时的view坐标（用来获取按下时view的大小）
private int oriLeft;
private int oriRight;
private int oriTop;
private int oriBottom;
private float baseValue;
private DragListener dragListener;
float originalScale;
private static final int TOUCH_NONE = 0x00;
private static final int TOUCH_ONE = 0x20;
private static final int TOUCH_TWO = 0x21;
/**
* 当前触摸模式：
* 无触摸；
* 单指触摸；
* 双指触摸；
*/
private int currentTouchMode = TOUCH_NONE ;
/**
* 是否开启：双指触摸缩放
*/
private boolean touchTwoZoomEnable = true;
/**
* 是否取消：触摸移动
*/
private boolean isCancleTouchDrag = false;
/**
* 产生效果的view（缩放、拖拽效果）
*/
private View mEffectView ;
/**
* 控制是否开启两指触摸缩放
* @param touchTwoZoomEnable
*/
public DragTouchListener setTouchTwoZoomEnable(boolean touchTwoZoomEnable) {
this.touchTwoZoomEnable = touchTwoZoomEnable;
return this;
}
/**
* 设置：是否取消拖拽移动
* @param cancleTouchDrag
*/
public DragTouchListener setCancleTouchDrag(boolean cancleTouchDrag) {
isCancleTouchDrag = cancleTouchDrag;
return this;
}
public interface DragListener {
void actionDown(View v);
void actionUp(View v);
void dragging(View listenerView, int left, int top, int right, int bottom);
void zooming(float scale);
}
// public void setDragListener(DragListener dragListener) {
// this.dragListener = dragListener;
// }
// public DragTouchListener(DisplayMetrics dm) {
// this.dm = dm;
// maxWidth = dm.widthPixels;
// maxHeight = dm.heightPixels - 50;
// }
public DragTouchListener(final ViewGroup limitParent,DragListener dragListener) {
// maxHeight = viewGroup.getHeight();
// maxWidth = viewGroup.getWidth();
this(limitParent);
this.dragListener = dragListener;
}
public DragTouchListener(){
this(null);
}
/**
*
* @param limitParent 拖动限制区域，防止移出屏幕(null:拖动无限制)
*/
public DragTouchListener(final ViewGroup limitParent) {
if (limitParent !=null) {
ViewTreeObserver vto = limitParent.getViewTreeObserver();
vto.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
@Override
public boolean onPreDraw() {
maxHeight = limitParent.getMeasuredHeight();
maxWidth = limitParent.getMeasuredWidth();
// Log.i("TAG", "maxHeight: "+maxHeight+", maxWidth"+maxWidth);
return true;
}
});
}
dragListener = new DragListener() {
@Override
public void actionDown(View v) {
}
@Override
public void actionUp(View v) {
}
@Override
public void dragging(View listenerView, int left, int top, int right, int bottom) {
}
@Override
public void zooming(float scale) {
}
};
}
private boolean moveFlag ;
@Override
public boolean onTouch(View v, MotionEvent event) {
// int action = event.getAction();
int action = event.getAction()& MotionEvent.ACTION_MASK;
// Log.i("TAG", "Touch:"+action);
//屏蔽父控件拦截onTouch事件
v.getParent().requestDisallowInterceptTouchEvent(true);
switch (action) {
case MotionEvent.ACTION_DOWN:
dragListener.actionDown(v);
lastX = (int) event.getRawX();
lastY = (int) event.getRawY();
oriLeft = v.getLeft();
oriRight = v.getRight();
oriTop = v.getTop();
oriBottom = v.getBottom();
currentTouchMode = TOUCH_ONE;
baseValue = 0;
lastScale = 1;
// originalScale = v.getScaleX();
break;
case MotionEvent.ACTION_POINTER_DOWN://多指触摸
oriLeft = v.getLeft();
oriRight = v.getRight();
oriTop = v.getTop();
oriBottom = v.getBottom();
currentTouchMode = TOUCH_TWO;
baseValue = 0;
lastScale = 1 ;
break;
/**
* layout(l,t,r,b)
* l Left position, relative to parent
t Top position, relative to parent
r Right position, relative to parent
b Bottom position, relative to parent
* */
case MotionEvent.ACTION_MOVE:
moveFlag = !moveFlag;
if (event.getPointerCount() == 2) {
// if (currentTouchMode == TOUCH_TWO ) {
if (touchTwoZoomEnable) {
float x = event.getX(0) - event.getX(1);
float y = event.getY(0) - event.getY(1);
// Log.i("TAG", "---y:点1: "+event.getY(0)+" 点2: "+event.getY(1));
float value = (float) Math.sqrt(x * x + y * y);// 计算两点的距离
if (baseValue == 0) {
baseValue = value;
// Log.i("TAG"," value: "+value+" ; baseValue: "+baseValue);
} else {
if ((value - baseValue) >= 10 || value - baseValue <= -10) {
// 当前两点间的距离 除以 手指落下时两点间的距离就是需要缩放的比例。
float scale = value / baseValue;
// Log.i("TAG", "onTouch-scale: "+scale+" value: "+value+" ; baseValue: "+baseValue);
//缩放view(不能用当前touch方法里的view，会造成频闪效果)（只能在其他view调用）
// mEffectView.setScaleX(scale);
// mEffectView.setScaleY(scale);
//改变大小进行缩放（只能缩放当前view的大小，如果是父布局，则里面的子控件无法缩小）
touchZoom(v,scale);
this.dragListener.zooming(scale);
}
}
}
} else if (currentTouchMode == TOUCH_ONE) {//1个手指
//如果取消拖拽，触摸就交给系统处理
if(isCancleTouchDrag){
return false;
}
//移动图片位置
touchDrag(v, event);
}
break;
case MotionEvent.ACTION_UP:
baseValue = 0;
dragListener.actionUp(v);
break;
default:
currentTouchMode = TOUCH_NONE;
break;
}
return true;
}
private float lastScale = 1;
/**
* 缩放view
* @param v
* @param scale 当前距离按下时的比例 (0.8：缩小到0.8倍)
*/
private void touchZoom(View v,float scale){
int oriWidth = Math.abs(oriRight - oriLeft);
int oriHeight = Math.abs(oriBottom - oriTop);
// if(lastScale == 0)lastScale = scale;
//需要缩放的比例（1-0.9=0.1，需要缩小0.1倍；-0.1：放大0.1倍）
float zoomScale = (lastScale - scale);
int dx = (int) (oriWidth*zoomScale/2f);
int dy = (int) (oriHeight*zoomScale/2f);
// Log.i("TAG", "---------------zoomScale: "+zoomScale);
// Log.i("TAG", "--------------------------dx: "+dx);
int left = v.getLeft() + dx;
int top = v.getTop() + dy;
int right = v.getRight() - dx;
int bottom = v.getBottom() - dy;
v.layout(left, top, right, bottom);
lastScale = scale;
}
private void touchDrag(View v, MotionEvent event) {
int dx = (int) event.getRawX() - lastX;
int dy = (int) event.getRawY() - lastY;
int left = v.getLeft() + dx;
int top = v.getTop() + dy;
int right = v.getRight() + dx;
int bottom = v.getBottom() + dy;
if (maxWidth !=0 && maxHeight!=0) {
//防止移出屏幕
if(left < 0){
left = 0;
right = left + v.getWidth();
}
if(right > maxWidth){
right = maxWidth;
left = right - v.getWidth();
}
if(top < 0){
top = 0;
bottom = top + v.getHeight();
}
if(bottom > maxHeight){
bottom = maxHeight;
top = bottom - v.getHeight();
}
}
v.layout(left, top, right, bottom);
dragListener.dragging(v, left, top, right, bottom);
// Log.i("TAG", "position" + left +", " + top + ", " + right + ", " + bottom);
lastX = (int) event.getRawX();
lastY = (int) event.getRawY();
}
}