getSupportFragmentManager().getFragments() shows a

问题:

Calling getSupportFragmentManager().getFragments() shows a compile time error with the message below:

getSupportFragmentManager().getFragments() can only be called from within the same library group(groupId = com.android.support)

I have imported the following classes in MainActivity:

import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.design.widget.BottomNavigationView;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.MenuItem;
import android.widget.Toast;

MainActivity extends AppCompatActivity.

My project module level build.gradle file is as follows:

apply plugin: 'com.android.application'

android {
    compileSdkVersion 25
    buildToolsVersion "25.0.2"
    defaultConfig {
        applicationId "com.mycompany.floatingdemo"
        minSdkVersion 16
        targetSdkVersion 25
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
        vectorDrawables.useSupportLibrary = true
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    compile 'com.android.support:appcompat-v7:25.2.0'
    compile 'com.android.support:design:25.2.0'
    compile 'com.android.support:support-vector-drawable:25.2.0'
    testCompile 'junit:junit:4.12'
}

This is the source code for the method getFragments inside FragmentManager.java.

/**
 * Get a list of all fragments that have been added to the fragment manager.
 *
 * @return The list of all fragments or null if none.
 * @hide
 */
@RestrictTo(LIBRARY_GROUP)
public abstract List<Fragment> getFragments();

I have recently updated my Android Studio to the latest stable version (2.3) and updated the Android Gradle plugin as well. I think this may be relevant because I have not previously seen this error.

回答1:

As noticeable in the FragmentManager documentation, getFragments() is not a public method available to apps, but an internal implementation detail of the Support Library, hence the use of the RestrictTo annotation that was added to prevent usage of private APIs.

You'll want to change your code to not use getFragments and only use the public APIs.

回答2:

Alternative For those who may be using getFragments() in their coding, I have replaced my code to get last fragment in backstack to this code(I am using this code in onBackPressed() to apply changes according to currentFragment assumed all fragments are added to backstack):

FragmentManager.BackStackEntry backStackEntryAt = getSupportFragmentManager().getBackStackEntryAt(getSupportFragmentManager().getBackStackEntryCount() - 1);
currentFragment = backStackEntryAt.getName();

回答3:

You can use （make sure using 25.2.0 or higher ）

supportFragmentManager.registerFragmentLifecycleCallbacks(object : FragmentManager.FragmentLifecycleCallbacks() {
    override fun onFragmentAttached(fm: FragmentManager?, f: Fragment?, context: Context?) {
        f?.let { fList.add(it) }
    }

    override fun onFragmentDetached(fm: FragmentManager?, f: Fragment?) {
        f?.let { fList.remove(it) }
    }

}, false) 

Instead of using getFragments()