详解android6.0版本下悬浮窗实现

public class MainActivity extends AppCompatActivity {
  private static final int ALERT_WINDOW_PERMISSION_CODE = 100;
  private Button start_float;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    start_float = (Button) findViewById(R.id.start_float);
    this.start_float.setOnClickListener(new View.OnClickListener() {
      @Override
      public void onClick(View view) {
        if (Build.VERSION.SDK_INT > 22) {
          sdk23Permission();
        } else {
          startService(new Intent(MainActivity.this, FloatService.class));
          finish();
        }
      }
    });
  }

  /**
   * @description 安卓6.0下权限处理
   * @author ldm
   * @time 2017/3/20 15:00
   */
  public void sdk23Permission() {
    if (!Settings.canDrawOverlays(this)) {
      Toast.makeText(MainActivity.this, "当前无权限使用悬浮窗，请授权！", Toast.LENGTH_SHORT).show();
      Intent intent = new Intent(Settings.ACTION_MANAGE_OVERLAY_PERMISSION,
          Uri.parse("package:" + getPackageName()));
      startActivityForResult(intent, ALERT_WINDOW_PERMISSION_CODE);
    } else {
      startService(new Intent(MainActivity.this, FloatService.class));
      finish();
    }
  }

  /**
   * 用户返回
   */
  protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (requestCode == ALERT_WINDOW_PERMISSION_CODE) {
      if (!Settings.canDrawOverlays(this)) {
        Toast.makeText(MainActivity.this, "权限授予失败，无法开启悬浮窗", Toast.LENGTH_SHORT).show();
      } else {
        startService(new Intent(MainActivity.this, FloatService.class));
        finish();
      }

    }
  }
}

public class FloatService extends Service {
  @Nullable
  @Override
  public IBinder onBind(Intent intent) {
    return null;
  }

  @Override
  public void onCreate() {
    FloatViewUtils.getInstance(this).addFloatView();
    super.onCreate();
  }
}

public class FloatView extends View {
  public static final int WIDTH = 150;
  public static final int HEIGHT = 150;
  private Paint circlePaint;
  private Paint textPaint;
  private static final String text = "50%";

  public FloatView(Context context) {
    this(context, null, 0);
  }

  public FloatView(Context context, @Nullable AttributeSet attrs) {
    this(context, attrs, 0);
  }

  public FloatView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    initPaints();
  }

  /**
   * @description 初始化相关画笔Paint
   * @author ldm
   * @time 2017/3/20
   */
  private void initPaints() {
    circlePaint = new Paint();
    circlePaint.setAntiAlias(true);
    circlePaint.setColor(Color.GRAY);
    textPaint = new Paint();
    //设置抗锯齿
    textPaint.setAntiAlias(true);
    //设置字体大小
    textPaint.setTextSize(30);
    //设置颜色
    textPaint.setColor(Color.WHITE);
    //设置（仿）粗体
    textPaint.setFakeBoldText(true);
  }

  @Override
  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    setMeasuredDimension(WIDTH, HEIGHT);
  }

  @Override
  protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    canvas.drawCircle(WIDTH / 2, HEIGHT / 2, WIDTH / 2, circlePaint);
    float textWidth = textPaint.measureText(text);
    float x = WIDTH / 2 - textWidth / 2;
    Paint.FontMetrics fms = textPaint.getFontMetrics();
    float dy = -(fms.descent + fms.ascent) / 2;
    float y = HEIGHT / 2 + dy;
    canvas.drawText(text, x, y, textPaint);
  }
}

public class FloatViewUtils {
  private static FloatViewUtils instance;
  private Context mContext;
  private WindowManager manager;
  private FloatView floatView;

  private FloatViewUtils(Context mContext) {
    this.mContext = mContext;
    manager = (WindowManager) mContext.getSystemService(Context.WINDOW_SERVICE);
    floatView = new FloatView(mContext);
  }

  public static FloatViewUtils getInstance(Context mContext) {
    if (null == instance) {
      synchronized (FloatViewUtils.class) {
        if (null == instance) {
          instance = new FloatViewUtils(mContext);
        }
      }
    }
    return instance;
  }

  public void addFloatView() {
    WindowManager.LayoutParams lp = new WindowManager.LayoutParams();
    //悬浮窗口大小
    lp.width = floatView.WIDTH;
    lp.height = floatView.HEIGHT;
    // 调整悬浮窗口位置
    lp.gravity = Gravity.LEFT | Gravity.CENTER;
    // 以屏幕左上角为原点，设置x、y初始值
//    lp.x = 0;
//    lp.y = 0;
    //设置悬浮窗口类型
    lp.type = WindowManager.LayoutParams.TYPE_PHONE;
    //设置悬浮窗口不接受焦点及触摸事件
    lp.flags = WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE | WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE;
    //设置图片格式，效果为背景透明
    lp.format = PixelFormat.RGBA_8888;
    manager.addView(floatView, lp);
  }
}