一.原理：
1.原理就是重寫(xiě)onTouchEvent方法帅矗，通過(guò)ACTION_DOWN惹资，ACTION_MOVE哮兰，ACTION_UP毛萌，處理按下移動(dòng)拿開(kāi)改變view的位置。
2.需要注意的是喝滞，在大部分情況下都會(huì)出現(xiàn)父容器重繪阁将，當(dāng)view的位置發(fā)生改變時(shí)，也要相應(yīng)改變其layoutparams右遭，否則父布局重繪時(shí)做盅，由于view的layoutparams沒(méi)發(fā)生改變導(dǎo)致重繪的時(shí)候view會(huì)回到原點(diǎn)或在xml布局設(shè)置的原始位置，所 以在改變view的位置同時(shí)窘哈，還要設(shè)置其layoutparams吹榴。
二.代碼：
```
public class MyImage extends ImageView {
private static final String TAG = "MyImage";
private Context mContext;
private int screenWidth;//屏幕寬高
private int screenHeight;
private int mLastX;
private int mLastY;
private int mLeft;//相對(duì)于父控件的位置
private int mTop;
private int mRight;
private int mBottom;
private int startX;//起始觸摸位置,為了判斷處理事件響應(yīng)
private int startY;
public MyImage(Context context) {
super(context);
mContext = context;
}
public MyImage(Context context, AttributeSet attrs) {
super(context, attrs);
mContext = context;
}
public MyImage(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
mContext = context;
}
/**
* 設(shè)置 父容器 寬高
* @param w
* @param h
*/
public void initWH(int w,int h){
this.screenWidth = w;
this.screenHeight = h;
}
@Override
public boolean onTouchEvent(MotionEvent event) {
int measuredHeight = this.getMeasuredHeight();//view自身高度
int measuredWidth = this.getMeasuredWidth();
int action = event.getAction();
switch (action) {
case MotionEvent.ACTION_DOWN:
startX = mLastX = (int) event.getRawX();
startY = mLastY = (int) event.getRawY();
break;
case MotionEvent.ACTION_MOVE:
int dx = (int) event.getRawX() - mLastX;
int dy = (int) event.getRawY() - mLastY;
//得到控件坐標(biāo)距離父控件原點(diǎn)(左上角，坐標(biāo)（0滚婉，0）)的x軸距離
mLeft = this.getLeft() + dx;
//以此類(lèi)推
mTop = this.getTop() + dy;
mRight = this.getRight() + dx;
mBottom = this.getBottom() + dy;
if (mLeft screenWidth) {
mRight = screenWidth;
mLeft = mRight - measuredWidth;
}
if (mTop screenHeight){
mBottom = screenHeight;
mTop = mBottom - measuredHeight;
}
int marginRight = screenWidth - mRight;
int marginBottom = screenHeight - mBottom;
ViewGroup.MarginLayoutParams params = (ViewGroup.MarginLayoutParams) this.getLayoutParams();
params.rightMargin = marginRight;
params.bottomMargin = marginBottom;
this.layout(mLeft, mTop, mRight, mBottom);
mLastX = (int) event.getRawX();
mLastY = (int) event.getRawY();
break;
case MotionEvent.ACTION_UP:
int endX = (int) event.getRawX();
int endY = (int) event.getRawY();
//判斷移動(dòng)的距離 極短 即為點(diǎn)擊事件
if (Math.abs(endX - startX) < 3 || Math.abs(endY - startY) < 3) {
if(listener != null){
listener.click(this);
}
}
break;
}
return true;
}
//自定義一個(gè)點(diǎn)擊事件
public interface MyOnClickListener{
void click(View view);
}
private MyOnClickListener listener;
public void setMyOnClickListener(MyOnClickListener listener){
this.listener = listener;
}
```
4.為了模擬父容器重繪的情況图筹，布局文件中添加一個(gè)listview 及SwipeRefreshLayout，父布局就是一個(gè)相對(duì)布局让腹，我們要拖動(dòng)的imageView初始設(shè)置在右下角远剩，布局文件就不貼出了。
5.在MainActivity中骇窍，獲取RelativeLayout 對(duì)象瓜晤，當(dāng)界面獲取焦點(diǎn)時(shí)，獲取容器的寬高腹纳。再調(diào)用MyImage中的初始化父容器高度痢掠。
```
private int containerHeight;//父容器高度
private int containerWidth;//父容器寬度
@Override
public void onWindowFocusChanged(boolean hasFocus) {
super.onWindowFocusChanged(hasFocus);
// 這里來(lái)獲取容器的寬和高
if (hasFocus) {
containerHeight = relativeLayout.getHeight();
containerWidth = relativeLayout.getWidth();
imageView.initWH(containerWidth,containerHeight);
}
}
```
6.為view設(shè)置點(diǎn)擊事件驱犹。由于在重寫(xiě)onTouchEvent時(shí)，事件被攔截足画，使用我們自定義的觸發(fā)事件
```
imageView.setMyOnClickListener(new MyImage.MyOnClickListener() {
@Override
public void click(View view) {
Log.e(TAG,"點(diǎn)擊了");
}
});
```
三.總結(jié):
在ACTION_MOVE處理view移動(dòng)時(shí)雄驹，首先要判斷是否滑出窗體，最重要的分清view的layout與LayoutParams,layout是view相對(duì)容器的左上角(0,0)位置锌云，layoutParams是view相對(duì)于容器的左上右下的位置
