package im.weiyuan.com.viewutils;

import android.content.Intent;

import android.os.PersistableBundle;

import android.support.v7.app.AppCompatActivity;

import android.os.Bundle;

import android.util.Log;

import android.view.MotionEvent;

import android.view.View;

import android.widget.Button;

import android.widget.ImageView;

import android.widget.LinearLayout;

import android.widget.RelativeLayout;

import android.widget.TextView;

import android.widget.Toast;

public class MainActivity extends AppCompatActivity  implements View.OnTouchListener{

    private ImageView iv_main;

    private RelativeLayout parentView;

    private int lastX;

    private int lastY;

    private int maxRight;

    private int maxBottom;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        iv_main = (ImageView) findViewById(R.id.iv_main);

        parentView = (RelativeLayout) iv_main.getParent();

  /*

  int right = parentView.getRight(); //0

  int bottom = parentView.getBottom(); //0

  Toast.makeText(this, right+"---"+bottom, 1).show();

  */

        //设置touch监听

        iv_main.setOnTouchListener(this);

    }

    @Override

    public boolean dispatchTouchEvent(MotionEvent ev) {

        Log.d("123456","activity dispatchTouchEvent is called" +ev.getAction());

        return super.dispatchTouchEvent(ev);

    }

    @Override

    public boolean onTouchEvent(MotionEvent event) {

        Log.d("123456","activity onTouchEvent  is called"+event.getAction());

        return super.onTouchEvent(event);

    }

    @Override

    public boolean onTouch(View v, MotionEvent event) {

        //得到事件的坐标

        int eventX = (int) event.getRawX();

        int eventY = (int) event.getRawY();

        switch (event.getAction()) {

            case MotionEvent.ACTION_DOWN:

                //得到父视图的right/bottom

                if(maxRight==0) {//保证只赋一次值

                    maxRight = parentView.getRight();

                    maxBottom = parentView.getBottom();

                }

                //第一次记录lastX/lastY

                lastX =eventX;

                lastY = eventY;

                break;

            case MotionEvent.ACTION_MOVE:

                //计算事件的偏移

                int dx = eventX-lastX;

                int dy = eventY-lastY;

                //根据事件的偏移来移动imageView

                int left = iv_main.getLeft()+dx;

                int top = iv_main.getTop()+dy;

                int right = iv_main.getRight()+dx;

                int bottom = iv_main.getBottom()+dy;

                //限制left >=0

                if(left<0) {

                    right += -left;

                    left = 0;

                }

                //限制top

                if(top<0) {

                    bottom += -top;

                    top = 0;

                }

                //限制right <=maxRight

                if(right>maxRight) {

                    left -= right-maxRight;

                    right = maxRight;

                }

                //限制bottom <=maxBottom

                if(bottom>maxBottom) {

                    top -= bottom-maxBottom;

                    bottom = maxBottom;

                }

                iv_main.layout(left, top, right, bottom);

                //再次记录lastX/lastY

                lastX = eventX;

                lastY = eventY;

                break;

            default:

                break;

        }

        return true;//所有的motionEvent都交给imageView处理

    }

}

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:tools="http://schemas.android.com/tools"

    android:layout_width="match_parent"

    android:layout_height="match_parent" >

    <ImageView

        android:id="@+id/iv_main"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:src="@mipmap/ic_launcher"/>

</RelativeLayout>