要想实现悬浮窗口，首先得有“android.permission.SYSTEM_ALERT_WINDOW”的权限，然后参数如下：

WindowManager.LayoutParams params = new WindowManager.LayoutParams();
//设置窗口类型在所有窗口之上
params.type = WindowManager.LayoutParams.TYPE_SYSTEM_OVERLAY;
params.flags = WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL | WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE;

如果没有params.flags这句话的话，在生成悬浮窗口后，悬浮窗口后的界面上东西都不能点。这句话的目的是让悬浮窗口失去焦点。简单封装成一个视图，直接new就可以使用了。

package com.androidtouch;
import android.content.Context;
import android.graphics.Rect;
import android.view.Gravity;
import android.view.MotionEvent;
import android.view.View;
import android.view.WindowManager;
public class FloatView extends View {
	private float mTouchX;
	private float mTouchY;
	private float x;
	private float y;
	private float mStartX;
	private float mStartY;
	private OnClickListener mClickListener;
	private WindowManager windowManager;
	private WindowManager.LayoutParams windowManagerParams;;
	public FloatView(Context context) {
		super(context);
		windowManager = (WindowManager) getContext().getApplicationContext()
				.getSystemService(Context.WINDOW_SERVICE);
		windowManagerParams = new WindowManager.LayoutParams();
		windowManagerParams.flags = WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE
				| WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL;
		windowManagerParams.type = WindowManager.LayoutParams.TYPE_SYSTEM_ALERT
				| WindowManager.LayoutParams.TYPE_SYSTEM_OVERLAY;
		windowManagerParams.format = 1;
		windowManagerParams.gravity = Gravity.LEFT | Gravity.TOP;
		windowManagerParams.height = Dp2Px(64);
		windowManagerParams.width = Dp2Px(64);
		windowManager.addView(this, windowManagerParams);
	}
	@Override
	public boolean onTouchEvent(MotionEvent event) {
		// 获取到状态栏的高度
		Rect frame = new Rect();
		getWindowVisibleDisplayFrame(frame);
		int statusBarHeight = frame.top;
		// 获取相对屏幕的坐标，即以屏幕左上角为原点
		x = event.getRawX();
		y = event.getRawY() - statusBarHeight; // statusBarHeight是系统状态栏的高度
		switch (event.getAction()) {
		case MotionEvent.ACTION_DOWN: // 捕获手指触摸按下动作
			// 获取相对View的坐标，即以此View左上角为原点
			mTouchX = event.getX();
			mTouchY = event.getY();
			mStartX = x;
			mStartY = y;
			break;
		case MotionEvent.ACTION_MOVE: // 捕获手指触摸移动动作
			updateViewPosition();
			break;
		case MotionEvent.ACTION_UP: // 捕获手指触摸离开动作
			updateViewPosition();
			mTouchX = mTouchY = 0;
			if ((x - mStartX) < 5 && (y - mStartY) < 5) {
				if (mClickListener != null) {
					mClickListener.onClick(this);
				}
			}
			break;
		}
		return true;
	}
	@Override
	public void setOnClickListener(OnClickListener l) {
		this.mClickListener = l;
	}
	private void updateViewPosition() {
		// 更新浮动窗口位置参数
		windowManagerParams.x = (int) (x - mTouchX);
		windowManagerParams.y = (int) (y - mTouchY);
		windowManager.updateViewLayout(this, windowManagerParams); // 刷新显示
	}
	public int Dp2Px(float dp) {
		final float scale = getContext().getResources().getDisplayMetrics().density;
		return (int) (dp * scale + 0.5f);
	}
	public int Px2Dp(float px) {
		final float scale = getContext().getResources().getDisplayMetrics().density;
		return (int) (px / scale + 0.5f);
	}
}

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