在获得许可后启动片段

Question

只有当用户授予存储权限时，我才希望从活动中启动片段。我的主要活动布局如下

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/root_container"
android:fitsSystemWindows="true"
android:background="@drawable/splash_gradient">
</FrameLayout>

现在，这个布局将在主活动开始时显示。我设置了代码以获得存储许可。并且希望用我的片段布局来替换这个布局，但是只有在当前授予存储权限之后，它才能正常工作，我的片段正在加载，除了我的片段在授予权限之前启动之外。是否有任何方法在权限函数上设置回调方法，并仅在权限被授予时启动该片段？

我的onCreate方法看起来就像

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.root_container);
    boolean b = getPermission();
    if(b ==true){
        HomeFragment fragment = new HomeFragment();
        FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
        transaction.replace(R.id.root_container, fragment).commit();
    }
    else getPermission();
}

我的get权限方法如下所示

    public boolean getPermission() {
    boolean f = false;
    //Check for SDK Version if greater than 23 then seek user permission
    if(Build.VERSION.SDK_INT>=23) {
        //Check whether permission is already granted
        if (ContextCompat.checkSelfPermission(this, Manifest.permission.READ_EXTERNAL_STORAGE)
                != PackageManager.PERMISSION_GRANTED) {
           // Ask for user permission
                ActivityCompat.requestPermissions(this,
                    new String[]{Manifest.permission.READ_EXTERNAL_STORAGE}, 404);
            if(ContextCompat.checkSelfPermission(this, Manifest.permission.READ_EXTERNAL_STORAGE)
                    !=PackageManager.PERMISSION_DENIED)
                f = true;
        }
        else f = true;
    }
    return f;
}

当我授予权限时，getPermission返回true，但是当应用程序第一次运行时，它甚至在获得getPermission()方法的结果之前就启动了片段，并且当我第二次运行应用程序时，它会显示片段布局。

Answer 1

您应该使用onRequestPermissionsResult来处理结果：

private static final int REQUEST_CODE = 404;

@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
    // Your code

    if (savedInstanceState == null) {
        tryToOpenHomeFragment();
    }
}

private void tryToOpenHomeFragment() {
    if (ContextCompat.checkSelfPermission(this, Manifest.permission.READ_EXTERNAL_STORAGE) == PackageManager.PERMISSION_GRANTED) {
        showHomeFragment();
    } else {
        ActivityCompat.requestPermissions(this,
                new String[]{Manifest.permission.READ_EXTERNAL_STORAGE}, REQUEST_CODE);
    }
}

@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
    super.onRequestPermissionsResult(requestCode, permissions, grantResults);
    if (requestCode == REQUEST_CODE) {
        if (grantResults.length == 1 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
            showHomeFragment();
        } else {
            // Permission was not granted
        }
    }
}

private void showHomeFragment() {
    HomeFragment fragment = new HomeFragment();
    getSupportFragmentManager()
            .beginTransaction()
            .replace(R.id.root_container, fragment)
            .commit();
}

Answer 2

您需要做的是:当许可被授予时，打开。

@Override
public void onRequestPermissionsResult(int requestCode,
    String permissions[], int[] grantResults) {
switch (requestCode) {
    case READ_EXTERNAL_STORAGE: {
        // If request is cancelled, the result arrays are empty.
        if (grantResults.length > 0
            && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
            // permission was granted
            HomeFragment fragment = new HomeFragment();
            FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
            transaction.replace(R.id.root_container, fragment).commit();
        } else {

            // permission denied, boo! Disable the
            // functionality that depends on this permission.

        }
        return;
    }
}

按照https://developer.android.com/training/permissions/requesting上的示例，检查权限是否被授予。