mobileCyberGamesApp/android/app/src/main/java/com/izouma/mobilecybergames/FloatWindowService.java

package com.izouma.mobilecybergames;

import android.app.Service;
import android.content.Intent;
import android.graphics.Color;
import android.graphics.PixelFormat;
import android.os.Build;
import android.os.IBinder;
import android.provider.Settings;
import android.support.annotation.Nullable;
import android.view.Gravity;
import android.view.MotionEvent;
import android.view.View;
import android.view.WindowManager;
import android.widget.Button;

public class FloatWindowService extends Service {
    private WindowManager              windowManager;
    private WindowManager.LayoutParams layoutParams;

    @Override
    public void onCreate() {
        super.onCreate();
        windowManager = (WindowManager) getSystemService(WINDOW_SERVICE);
        layoutParams = new WindowManager.LayoutParams();
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            layoutParams.type = WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY;
        } else {
            layoutParams.type = WindowManager.LayoutParams.TYPE_PHONE;
        }
        layoutParams.format = PixelFormat.RGBA_8888;
        layoutParams.gravity = Gravity.LEFT | Gravity.TOP;
        layoutParams.flags = WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL | WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE;
        layoutParams.width = 500;
        layoutParams.height = 100;
        layoutParams.x = 300;
        layoutParams.y = 300;
    }

    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {//判断系统版本
            if (Settings.canDrawOverlays(this)) {
                Button button = new Button(getApplicationContext());
                button.setText("我是个button窗口");
                button.setBackgroundColor(Color.BLUE);
                windowManager.addView(button, layoutParams);

                button.setOnTouchListener(new FloatingOnTouchListener());
            }
        } else {
            Button button = new Button(getApplicationContext());
            button.setText("我是个button窗口");
            button.setBackgroundColor(Color.BLUE);
            windowManager.addView(button, layoutParams);

            button.setOnTouchListener(new FloatingOnTouchListener());
        }

        return super.onStartCommand(intent, flags, startId);
    }

    private class FloatingOnTouchListener implements View.OnTouchListener {
        private int x;
        private int y;

        @Override
        public boolean onTouch(View view, MotionEvent event) {
            switch (event.getAction()) {
                case MotionEvent.ACTION_DOWN:
                    x = (int) event.getRawX();
                    y = (int) event.getRawY();
                    break;
                case MotionEvent.ACTION_MOVE:
                    int nowX = (int) event.getRawX();
                    int nowY = (int) event.getRawY();
                    int movedX = nowX - x;
                    int movedY = nowY - y;
                    x = nowX;
                    y = nowY;
                    layoutParams.x = layoutParams.x + movedX;
                    layoutParams.y = layoutParams.y + movedY;
                    windowManager.updateViewLayout(view, layoutParams);
                    break;
                default:
                    break;
            }
            return false;
        }
    }
}