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