public Button mFloatingButton;
 
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
 
  //初始化view
  initView();
 }
 //初始化view
 private void initView() {
  mFloatingButton=(Button) findViewById(R.id.floating_btn);
  mFloatingButton.setOnClickListener(this);
 }
 
 public void startFloatingButtonService(View view) {
  Log.e("測試流程", "測試流程");
  if (FloatingService_Button.isStarted) {
   Log.e("測試流程2", "測試流程2");
   return;
  }
  if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {//判斷系統(tǒng)版本
   if (!Settings.canDrawOverlays(this)) {
    Toast.makeText(this, "當前無權限，請授權", Toast.LENGTH_SHORT);
    Log.e("測試流程3", "測試流程3");
    startActivityForResult(new Intent(Settings.ACTION_MANAGE_OVERLAY_PERMISSION, Uri.parse("package:" + getPackageName())), 0);
   } else {
    Log.e("測試流程4", "測試流程4");
    startService(new Intent(MainActivity.this, FloatingService_Button.class));
   }
  } else {
   startService(new Intent(MainActivity.this, FloatingService_Button.class));
  }
 
 }
 
 @Override
 protected void onActivityResult(int requestCode, int resultCode, Intent data) {
  if (requestCode == 0) {
   if (!Settings.canDrawOverlays(this)) {
    Log.e("測試流程5", "測試流程5");
    Toast.makeText(this, "授權失敗", Toast.LENGTH_SHORT).show();
   } else {
    Log.e("測試流程6", "測試流程6");
    Toast.makeText(this, "授權成功", Toast.LENGTH_SHORT).show();
    startService(new Intent(MainActivity.this, FloatingService_Button.class));
   }
  }
 }
 
 @Override
 public void onClick(View v) {
  switch (v.getId()){
   case R.id.floating_btn :
    startFloatingButtonService(v);
    break;
  }
 }

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 xmlns:tools="http://schemas.android.com/tools"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 android:orientation="vertical"
 tools:context="com.example.jack_lin.suspendwindow.MainActivity">
 
 <Button
  android:id="@+id/floating_btn"
  style="@style/floatingBtn"
  android:text="@string/floating_btn" />
 
 
</LinearLayout>

public static boolean isStarted = false;
 
 private WindowManager windowManager;
 private WindowManager.LayoutParams layoutParams;
 
 private Button button;
 
 @Override
 public void onCreate() {
  super.onCreate();
  Log.e("進入服務1", "進入服務1");
  isStarted = true;
  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) {
  Log.e("進入服務2", "進入服務2");
 
  return null;
 }
 
 @Override
 public int onStartCommand(Intent intent, int flags, int startId) {
  Log.e("進入服務3", "進入服務3");
  showFloatingWindow();
  return super.onStartCommand(intent, flags, startId);
 }
 
 private void showFloatingWindow() {
  if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {//判斷系統(tǒng)版本
   if (Settings.canDrawOverlays(this)) {
    button = new Button(getApplicationContext());
    button.setText("我是個button窗口");
    button.setBackgroundColor(Color.BLUE);
    windowManager.addView(button, layoutParams);
 
    button.setOnTouchListener(new FloatingOnTouchListener());
   }
  } else {
   button = new Button(getApplicationContext());
   button.setText("我是個button窗口");
   button.setBackgroundColor(Color.BLUE);
   windowManager.addView(button, layoutParams);
 
   button.setOnTouchListener(new FloatingOnTouchListener());
  }
 }
 
 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;
  }
 }

<uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW" />
<uses-permission android:name="android.permission.INTERNET" />