Android 简单实现控件的拖动

控件的拖动,使用到一个监听事件

setOnTouchListener:
XML代码:

 <?xml version="1.0" encoding="utf-8"?>
 <LinearLayout
     xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     tools:context=".MainActivity">

     <ImageView
         android:id="@+id/textview"
         android:src="@drawable/ic_launcher_foreground"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:background="@color/colorPrimaryDark"
         android:text="www.baidu.com"/>

 </LinearLayout>

JAVA代码

 package com.example.a11658.textviewdrag;

 import android.annotation.SuppressLint;
 import android.os.Bundle;
 import android.support.v7.app.AppCompatActivity;
 import android.view.MotionEvent;
 import android.view.View;
 import android.widget.ImageView;

 public class MainActivity extends AppCompatActivity {
     private ImageView tv;
     private int x;
     private int y;

     @SuppressLint("ClickableViewAccessibility")
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);

         tv = findViewById(R.id.textview);
         tv.setOnTouchListener(new View.OnTouchListener() {
             @Override
             public boolean onTouch(View v, MotionEvent event) {
                 switch (event.getAction()) {
                     case MotionEvent.ACTION_DOWN:
                         //手指按下
                         //获取第一次接触屏幕
                         x = (int) event.getRawX();
                         y = (int) event.getRawY();
                         break;
                     case MotionEvent.ACTION_MOVE:
                         //手指拖动
                         //获取距离差
                         int dx = (int) event.getRawX() - x;
                         int dy = (int) event.getRawY() - y;
                         //更改Imageview在窗体的位置
                         v.layout(v.getLeft() + dx, v.getTop() + dy,
                                 v.getRight() + dx, v.getBottom() + dy);
                         //获取移动后的位置
                         x = (int) event.getRawX();
                         y = (int) event.getRawY();
                         break;
                     case MotionEvent.ACTION_UP:
                         //手指弹起
                         x = (int) event.getRawX();
                         y = (int) event.getRawY();
                         break;
                 }
                 return true;
             }
         });
     }
 }

view.layout(left, top, right, bottom)实现拖动。

1.按下图搞懂几个坐标

视图宽度 view.getWidth();

视图高度 view.getHeight() 

橘色线：view.getLeft()

蓝色线：view.getRight()

红色线：view.getTop()

粉色线：view.getBottom()

上下左右的偏移都是相对于（0.0）来说

Demo地址：https://github.com/1165863642/WidgetDrag