Android 获取判断是否有悬浮窗权限的方法

现在很多应用都会用到悬浮窗，很多国产rom把悬浮窗权限加入控制了，你就需要判断是否有悬浮窗权限，然后做对应操作。

Android 原生有自带权限管理的，只是被隐藏了。看android源码在android.app下就有个AppOpsManager类。

类说明如下：

/**
* API for interacting with "application operation" tracking.
*
* <p>This API is not generally intended for third party application developers; most
* features are only available to system applications. Obtain an instance of it through
* {@link Context#getSystemService(String) Context.getSystemService} with
* {@link Context#APP_OPS_SERVICE Context.APP_OPS_SERVICE}.</p>
*/

上面说明了只对系统应用有用，rom厂商们应该就是利用这个AppOps机制开放一些权限控制。

我们要判断是否有权限该如何做呢？就只能通过反射去判断了。

AppOpsManager的checkOp方法，就是检测是否有某项权限的方法有这些返回值，分别是允许，忽略，错误和默认：

/**
* Result from {@link #checkOp}, {@link #noteOp}, {@link #startOp}: the given caller is
* allowed to perform the given operation.
*/
public static final int MODE_ALLOWED = 0;

/**
* Result from {@link #checkOp}, {@link #noteOp}, {@link #startOp}: the given caller is
* not allowed to perform the given operation, and this attempt should
* <em>silently fail</em> (it should not cause the app to crash).
*/
public static final int MODE_IGNORED = 1;

/**
* Result from {@link #checkOpNoThrow}, {@link #noteOpNoThrow}, {@link #startOpNoThrow}: the
* given caller is not allowed to perform the given operation, and this attempt should
* cause it to have a fatal error, typically a {@link SecurityException}.
*/
public static final int MODE_ERRORED = 2;

/**
* Result from {@link #checkOp}, {@link #noteOp}, {@link #startOp}: the given caller should
* use its default security check. This mode is not normally used; it should only be used
* with appop permissions, and callers must explicitly check for it and deal with it.
*/
public static final int MODE_DEFAULT = 3;

只有MODE_ALLOWED才是确定有权限的。

类里面checkOp方法如下，三个参数分别是操作id，uid和包名：

/**
* Do a quick check for whether an application might be able to perform an operation.
* This is <em>not</em> a security check; you must use {@link #noteOp(int, int, String)}
* or {@link #startOp(int, int, String)} for your actual security checks, which also
* ensure that the given uid and package name are consistent. This function can just be
* used for a quick check to see if an operation has been disabled for the application,
* as an early reject of some work. This does not modify the time stamp or other data
* about the operation.
* @param op The operation to check. One of the OP_* constants.
* @param uid The user id of the application attempting to perform the operation.
* @param packageName The name of the application attempting to perform the operation.
* @return Returns {@link #MODE_ALLOWED} if the operation is allowed, or
* {@link #MODE_IGNORED} if it is not allowed and should be silently ignored (without
* causing the app to crash).
* @throws SecurityException If the app has been configured to crash on this op.
* @hide
*/
public int checkOp(int op, int uid, String packageName) {
try {
 int mode = mService.checkOperation(op, uid, packageName);
 if (mode == MODE_ERRORED) {
  throw new SecurityException(buildSecurityExceptionMsg(op, uid, packageName));
 }
 return mode;
} catch (RemoteException e) {
}
return MODE_IGNORED;
}

操作id即op可以在该类中找到静态值定义，android23里面有62种权限，我们需要的是OP_SYSTEM_ALERT_WINDOW=24

知道这些就可以用反射把我们的方法写出了：

/**
 * 判断 悬浮窗口权限是否打开
 *
 * @param context
 * @return true 允许 false禁止
 */
public static boolean getAppOps(Context context) {
 try {
  Object object = context.getSystemService("appops");
  if (object == null) {
   return false;
  }
  Class localClass = object.getClass();
  Class[] arrayOfClass = new Class[3];
  arrayOfClass[0] = Integer.TYPE;
  arrayOfClass[1] = Integer.TYPE;
  arrayOfClass[2] = String.class;
  Method method = localClass.getMethod("checkOp", arrayOfClass);
  if (method == null) {
   return false;
  }
  Object[] arrayOfObject1 = new Object[3];
  arrayOfObject1[0] = Integer.valueOf(24);
  arrayOfObject1[1] = Integer.valueOf(Binder.getCallingUid());
  arrayOfObject1[2] = context.getPackageName();
  int m = ((Integer) method.invoke(object, arrayOfObject1)).intValue();
  return m == AppOpsManager.MODE_ALLOWED;
 } catch (Exception ex) {

}
 return false;
}

测试在魅族华为小米大部分机型上都是可以的，但这个方法也不能保证正确，一些机型上会返回错误即MODE_ERRORED，就是获取不到权限值，这个方法就返回了false，但实际上悬浮窗是可以使用的。

来源：https://blog.csdn.net/mzm489321926/article/details/50542065