女神.png

Android 6.0的權(quán)限不再是在安裝的時候一股腦給你了。需要權(quán)限的話，需要代碼中去獲取。而對于用戶，獲取權(quán)限會彈框，用戶可以醒目地知道應用拿了什么權(quán)限，用戶進而可以決定給不給這個權(quán)限。

例如下面的例子是一個垃圾程序要獲取短信的權(quán)限

獲取權(quán)限.png

在代碼只需要加一句就可以了,參數(shù)里面了的2我是隨便亂寫的，就是要輸入一個整形，代表request code。

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        this.requestPermissions(
                new String[]{Manifest.permission.SEND_SMS},
                2);
    }

這篇文章不說太多，就說下這個彈框是怎么出來的好了。
首先入口是Activity類，調(diào)用requestPermissions獲取權(quán)限?？梢钥吹剿麊恿肆硪粋€Activity?？梢韵胂?，這個彈框就是在這個Activity里面。我們看看這個Intent是什么，找出Intent的包名與Action。
/frameworks/base/core/java/android/app/Activity.java

    public final void requestPermissions(@NonNull String[] permissions, int requestCode) {
        Intent intent = getPackageManager().buildRequestPermissionsIntent(permissions);
        startActivityForResult(REQUEST_PERMISSIONS_WHO_PREFIX, intent, requestCode, null);
    }

通過ContextImpl.getPackageManager()獲取到的是ApplicationPackageManager，他的父類是PackageManager。
/frameworks/base/core/java/android/app/ContextImpl.java

    @Override
    public PackageManager getPackageManager() {
        if (mPackageManager != null) {
            return mPackageManager;
        }

        IPackageManager pm = ActivityThread.getPackageManager();
        if (pm != null) {
            // Doesn't matter if we make more than one instance.
            return (mPackageManager = new ApplicationPackageManager(this, pm));
        }

        return null;
    }

ApplicationPackageManager獲取到這個intent的action是android.content.pm.action.REQUEST_PERMISSIONS，包名要再看看，是通過getPermissionControllerPackageName()獲取的。
/frameworks/base/core/java/android/app/ApplicationPackageManager.java

    public static final String ACTION_REQUEST_PERMISSIONS =
            "android.content.pm.action.REQUEST_PERMISSIONS";
    public static final String EXTRA_REQUEST_PERMISSIONS_NAMES =
            "android.content.pm.extra.REQUEST_PERMISSIONS_NAMES";

    public Intent buildRequestPermissionsIntent(@NonNull String[] permissions) {
        if (ArrayUtils.isEmpty(permissions)) {
           throw new NullPointerException("permission cannot be null or empty");
        }
        Intent intent = new Intent(ACTION_REQUEST_PERMISSIONS);
        intent.putExtra(EXTRA_REQUEST_PERMISSIONS_NAMES, permissions);
        intent.setPackage(getPermissionControllerPackageName());
        return intent;
    }

getPermissionControllerPackageName()會進一步調(diào)用mPM.getPermissionControllerPackageName()，這個mPM是系統(tǒng)服務PackageManagerService的遠程代理。

    @Override
    public String getPermissionControllerPackageName() {
        synchronized (mLock) {
            if (mPermissionsControllerPackageName == null) {
                try {
                    mPermissionsControllerPackageName = mPM.getPermissionControllerPackageName();
                } catch (RemoteException e) {
                    throw new RuntimeException("Package manager has died", e);
                }
            }
            return mPermissionsControllerPackageName;
        }
    }

最后包名通過PackageManagerService的getRequiredInstallerLPr獲取到，看這個函數(shù)名，可以顧名思義下，就是安裝器，就是安裝apk那個玩意。

安裝器.png

    private String getRequiredInstallerLPr() {
        Intent installerIntent = new Intent(Intent.ACTION_INSTALL_PACKAGE);
        installerIntent.addCategory(Intent.CATEGORY_DEFAULT);
        installerIntent.setDataAndType(Uri.fromFile(new File("foo.apk")), PACKAGE_MIME_TYPE);

        final List<ResolveInfo> installers = queryIntentActivities(installerIntent,
                PACKAGE_MIME_TYPE, 0, 0);

        String requiredInstaller = null;

        final int N = installers.size();
        for (int i = 0; i < N; i++) {
            final ResolveInfo info = installers.get(i);
            final String packageName = info.activityInfo.packageName;

            if (!info.activityInfo.applicationInfo.isSystemApp()) {
                continue;
            }

            if (requiredInstaller != null) {
                throw new RuntimeException("There must be one required installer");
            }

            requiredInstaller = packageName;
        }

        if (requiredInstaller == null) {
            throw new RuntimeException("There must be one required installer");
        }

        return requiredInstaller;
    }

所以，最后的組合而成的intent的包名是com.android.packageinstaller，action是android.content.pm.action.REQUEST_PERMISSIONS。

應用安裝器.png

這個Action會啟動應用安裝器的GrantPermissionsActivity 進行授權(quán)

清單.png

所以啦，這個彈框是由GrantPermissionsActivity中彈出的。分析完畢！