Android 拖动组件

@(基本知识)[Android, View, ImageView]

一. 实现方式和场景

• 主要是有时候需要在页面上，需要悬浮的按钮可以拖动，吸附在屏幕左右2侧；

• 实现方式有两种方法，如下

  第一种方式：直接自定义组件，自定义ViewonTouch(View v, MotionEvent event)事件，通过View.layout(left,top,right,bottom)更新组件位置；

  第二种方式：悬浮窗模式实现，自定义组件将View添加到Window上面，实现onTouchEvent(MotionEvent event)，通过更新View在Window上面的位置来拖动组件(updateViewLayout)。

项目地址 ：https://github.com/fenggit/DragView

二. 实现方式（方式二）

package com.android.main;import android.content.Context;import android.graphics.Rect;import android.util.AttributeSet;import android.util.DisplayMetrics;import android.util.Log;import android.view.MotionEvent;import android.view.View;import android.view.ViewConfiguration;import android.widget.ImageView;/** * Author: river * Date: 2016/8/23 11:59 * Description: 拖动组件 * <p/> * getLeft：相对父布局 * getRawX：相对于屏幕 * getX：相对于自身View */public class DragView extends ImageView implements View.OnTouchListener {    private String TAG = DragView.class.getSimpleName();    /**     * 记录View与X轴的距离     */    private int mLastX;    /**     * 记录View与Y轴的距离     */    private int mLastY;    /**     * 屏幕宽度     */    private int mScreenWidth;    /**     * 屏幕高度     */    private int mScreenHeight;    /**     * 状态栏高度     */    private final static int STATUS_HEIGHT = 48;    /**     * View的距离     */    private int left, top, right, bottom;    /**     * 是否移动标记     */    private boolean isMove = false;    private int mTouchSlop = 0;    float mTouchX, mTouchY;    public DragView(Context context, AttributeSet attrs) {        super(context, attrs);        init(context);    }    public DragView(Context context) {        super(context);        init(context);    }    private void init(Context context) {        setClickable(true);        setOnTouchListener(this);        DisplayMetrics dm = context.getResources().getDisplayMetrics();        mScreenWidth = dm.widthPixels;        mScreenHeight = dm.heightPixels - STATUS_HEIGHT;        mTouchSlop = ViewConfiguration.get(context).getScaledTouchSlop();        Log.i(TAG, "mTouchSlop=" + mTouchSlop);//        Log.i(TAG, "w : h " + mScreenWidth + " : " + mScreenHeight);    }    int firstX;    @Override    public boolean onTouch(View v, MotionEvent event) {        int action = event.getAction();        switch (action) {            case MotionEvent.ACTION_DOWN:                isMove = false;                // 相对于屏幕的坐标点                mLastX = (int) event.getRawX();                mLastY = (int) event.getRawY();                // 相对于自身组件的坐标点                mTouchX = event.getX();                mTouchY = event.getY();                break;            case MotionEvent.ACTION_MOVE://                Log.d(TAG, "x  = " + (event.getX() - mTouchX) + "   Y = " + Math.abs(event.getY() - mTouchY));                // 滑动的最小距离                if ((Math.abs(event.getX() - mTouchX) > mTouchSlop) || (Math.abs(event.getY() - mTouchY) > mTouchSlop)) {//                    Log.d(TAG, "move");                    isMove = true;                    // 滑动距离                    int dx = (int) (event.getRawX() - mLastX);                    int dy = (int) (event.getRawY() - mLastY);                    left = v.getLeft() + dx;                    right = v.getRight() + dx;                    top = v.getTop() + dy;                    bottom = v.getBottom() + dy;                    // 下面判断移动是否超出屏幕                    if (left < 0) {                        left = 0;                        right = left + v.getWidth();                    }                    if (right > mScreenWidth) {                        right = mScreenWidth;                        left = right - v.getWidth();                    }                    if (top < 0) {                        top = 0;                        bottom = top + v.getHeight();                    }                    if (bottom > mScreenHeight) {                        bottom = mScreenHeight;                        top = bottom - v.getHeight();                    }//                Log.i(TAG, "left= " + left + ";top= " + top + ";right= " + right + ";bottom= " + bottom);                    v.layout(left, top, right, bottom);                    mLastX = (int) event.getRawX();                    mLastY = (int) event.getRawY();                    return true;                }                break;            case MotionEvent.ACTION_UP:                if (isMove) {                    Log.d(TAG, "左右吸附");                    isMove = false;                    // 左右吸附                    if (left > mScreenWidth / 2) {                        right = mScreenWidth;                        left = right - v.getWidth();                    } else {                        right = v.getWidth();                        left = 0;                    }                    // 上下吸附//                if (top > mScreenHeight / 2) {//                    top = mScreenHeight - v.getHeight();//                    bottom = mScreenHeight;//                } else {//                    top = 0;//                    bottom = v.getHeight();//                }                    v.layout(left, top, right, bottom);                    return true;                } else {//                    Log.d(TAG, "click");                }                mTouchX = mTouchY = 0;                break;        }        return false;    }    /**     * 获取到状态栏的高度     *     * @return     */    private int getStatusHeight() {        Rect frame = new Rect();        getWindowVisibleDisplayFrame(frame);        return frame.top;    }}