android 悬浮窗权限申请

在AndroidQ（12）中，如果应用尝试获取SYSTEM_ALERT_WINDOW权限，且设备被视为低内存设备时，系统会阻止该功能。可以通过修改ro.config.low_ram属性为false来避免这一限制，从而在设备上启用权限。

一问题描述：

预装应用到系统，应用有申请悬浮窗功能，点击去设置界面该应用下开启该开关，但是系统提示禁用该功能，截图如下：

二分析：

这是系统功能限制控制了该功能：

定位源码：android/packages/apps/Settings/src/com/android/settings/applications/manageapplications/ManageApplications.java

 @Overridepublic View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) {if (mListType == LIST_TYPE_OVERLAY && !Utils.isSystemAlertWindowEnabled(getContext())) {//Utils.isSystemAlertWindowEnabled(getContext())表示弹窗是否可用mRootView = inflater.inflate(R.layout.manage_applications_apps_unsupported, null);setHasOptionsMenu(false);return mRootView;}mRootView = inflater.inflate(R.layout.manage_applications_apps, null);mLoadingContainer = mRootView.findViewById(R.id.loading_container);mEmptyView = mRootView.findViewById(android.R.id.empty);mRecyclerView = mRootView.findViewById(R.id.apps_list);mApplications = new ApplicationsAdapter(mApplicationsState, this, mFilter,savedInstanceState);if (savedInstanceState != null) {mApplications.mHasReceivedLoadEntries =savedInstanceState.getBoolean(EXTRA_HAS_ENTRIES, false);mApplications.mHasReceivedBridgeCallback =savedInstanceState.getBoolean(EXTRA_HAS_BRIDGE, false);}

我们看下面的工具类

android/packages/apps/Settings/src/com/android/settings/Utils.java

 /** Get {@link Resources} by subscription id if subscription id is valid. */public static Resources getResourcesForSubId(Context context, int subId) {if (subId != SubscriptionManager.INVALID_SUBSCRIPTION_ID) {return SubscriptionManager.getResourcesForSubId(context, subId);} else {return context.getResources();}}
//********************start***********************/*** Returns true if SYSTEM_ALERT_WINDOW permission is available.* Starting from Q, SYSTEM_ALERT_WINDOW is disabled on low ram phones.*/public static boolean isSystemAlertWindowEnabled(Context context) {// SYSTEM_ALERT_WINDOW is disabled on on low ram devices starting from QActivityManager am = (ActivityManager) context.getSystemService(Context.ACTIVITY_SERVICE);return !(am.isLowRamDevice() && (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q));}
//*********************end************************/*** Adds a shadow appear/disappear animation to action bar scroll.** <p/>* This method must be called after {@link Fragment#onCreate(Bundle)}.*/public static void setActionBarShadowAnimation(Activity activity, Lifecycle lifecycle,View scrollView) {if (activity == null) {Log.w(TAG, "No activity, cannot style actionbar.");return;}final ActionBar actionBar = activity.getActionBar();if (actionBar == null) {

看上面的代码，该版本是否大于Q，且am.isLowRamDevice() 设备是否是低内存

我们接下来看android/frameworks/base/core/java/android/app/ActivityManager.java

/*** Returns true if this is a low-RAM device.  Exactly whether a device is low-RAM* is ultimately up to the device configuration, but currently it generally means* something with 1GB or less of RAM.  This is mostly intended to be used by apps* to determine whether they should turn off certain features that require more RAM.*/public boolean isLowRamDevice() {return isLowRamDeviceStatic();}/** @hide */@UnsupportedAppUsagepublic static boolean isLowRamDeviceStatic() {return RoSystemProperties.CONFIG_LOW_RAM ||(Build.IS_DEBUGGABLE && DEVELOPMENT_FORCE_LOW_RAM);}

我们看下面的/frameworks/base/core/java/com/android/internal/os/RoSystemProperties.java

    // ------ ro.config.* -------- //public static final boolean CONFIG_AVOID_GFX_ACCEL =SystemProperties.getBoolean("ro.config.avoid_gfx_accel", false);public static final boolean CONFIG_LOW_RAM =SystemProperties.getBoolean("ro.config.low_ram", false);public static final boolean CONFIG_SMALL_BATTERY =SystemProperties.getBoolean("ro.config.small_battery", false);// ------ ro.fw.* ------------ //public static final boolean FW_SYSTEM_USER_SPLIT =SystemProperties.getBoolean("ro.fw.system_user_split", false);public static final boolean MULTIUSER_HEADLESS_SYSTEM_USER =SystemProperties.getBoolean("ro.fw.mu.headless_system_user", false);

public static final boolean CONFIG_LOW_RAM =
            SystemProperties.getBoolean("ro.config.low_ram", false);

我们看到以上是从变量o.config.low_ram读取的，这样我们需要从属性文件中修改改默认值就可以了。

在build、device下检索，该属性，最后在build目录下找到。

三修改

修改点：

//build目录下
Date:   Fri Aug 15 11:40:32 2025 +0800关闭低内存系统禁用悬浮窗Change-Id: I784af2652c3a9426ec7eb9be023ffebb60318681diff --git a/target/product/go_defaults_common.mk b/target/product/go_defaults_common.mk
index 7f19615ed..5d384eff5 100644
--- a/target/product/go_defaults_common.mk
+++ b/target/product/go_defaults_common.mk
@@ -19,7 +19,7 @@# Set lowram options and enable traced by defaultPRODUCT_VENDOR_PROPERTIES += \
-     ro.config.low_ram=true \
+     ro.config.low_ram=false \# Speed profile services and wifi-service to reduce RAM and storage.PRODUCT_SYSTEM_SERVER_COMPILER_FILTER := speed-profile

四重新编译刷机，效果如下：

问题解决~

参考文章：

android 悬浮窗权限申请