Android可按住拖拉的View，懸浮窗拖拉效果

代碼如下：

package com.bg.sdk.floatwin;

import android.app.Activity;
import android.view.MotionEvent;
import android.view.ViewGroup;
import android.widget.ImageView;

import com.bg.sdk.common.BGUIHelper;

/**
 * @author ljj
 * @create-time 2019/9/10
 * @desc
 */
public class BGFloatView extends ImageView {
    private int screenWidth;
    private int screenHeight;

    public BGFloatView(Activity activity) {
        super(activity);
        setAlpha(0.8f);
        setImageResource(BGUIHelper.drawableID("ibiguo_float"));
        ViewGroup.LayoutParams viewParams = new ViewGroup.LayoutParams(
                100, 100);
        setLayoutParams(viewParams);

        ViewGroup contentView = activity.findViewById(android.R.id.content);
        screenWidth = contentView.getWidth();   //根據實際情況設置可移動的範圍
        screenHeight = contentView.getHeight();
    }

    float downX, downY;

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        super.onTouchEvent(event);
        if (this.isEnabled()) {
            switch (event.getAction()) {
                case MotionEvent.ACTION_DOWN:
                    downX = event.getRawX();
                    downY = event.getRawY();
                    break;
                case MotionEvent.ACTION_MOVE:
                    float x = getX() + (event.getRawX() - downX);
                    float y = getY() + (event.getRawY() - downY);
                    downX = event.getRawX();
                    downY = event.getRawY();
                    if (x < 0) {
                        x = 0;
                    }
                    if (y < 0) {
                        y = 0;
                    }
                    if (x >= screenWidth - getWidth()) {
                        x = screenWidth - getWidth();
                    }
                    if (y >= screenHeight - getHeight()) {
                        y = screenHeight - getHeight();
                    }
                    setX(x);
                    setY(y);
                    break;
            }
            return true;
        }
        return false;
    }

}

用法
        BGFloatView mFloatWin = new BGFloatView(activity);
        ViewGroup contentView = activity.findViewById(android.R.id.content);
        contentView.addView(mFloatWin);