相关疑难解决方法(0)

如何使用(或"我们可以使用")getChildFragmentManager()以编程方式(动态)添加Fragments？

这是我的例子.

我有一个MainActivity,一个OuterFrag和一个InnerFrag.我将动态添加OuterFrag到.而且,我还将动态添加到.但我想完全添加一个孩子,而不是替换,并成为新的孩子.MainActivityFragmentManagerInnerFragOuterFragFragmentManagerInnerFragOuterFragOuterFragMainActivity

我想保持这种等级制度:MainActivity -> OuterFrag -> InnerFrag.所以MainActivity总是可以调用OuterFrag.

但是不要从这个层次结构改变:MainActivity -> OuterFrag到这个层次结构:MainActivity -> InnerFrag这MainActivity将失去OuterFrag.

这是我的示例代码.

MainActivity.java

package com.example.frag;

import android.os.Bundle;
import android.support.v4.app.FragmentActivity;

public class MainActivity extends FragmentActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        getSupportFragmentManager().beginTransaction().add(R.id.frameLayout, new OuterFrag()).commit();
        getSupportFragmentManager().executePendingTransactions();

        System.out.println("Before: "
                + getSupportFragmentManager().findFragmentById(R.id.frameLayout));

        ((OuterFrag) getSupportFragmentManager().findFragmentById(R.id.frameLayout))
                .addInnerFrag();

        System.out.println("After: "
                + …

当我使用Google Play Services的v6.5.87时,我在调用时会收到空指针异常getMapAsync().我SupportMapFragment在我Fragment的xml布局中使用了一个.

我的代码:

SupportMapFragment mapFragment = (SupportMapFragment) getActivity()
        .getSupportFragmentManager().findFragmentById(R.id.mapFragment);

mapFragment.getMapAsync(this);

注意:调用getMap()较旧的Google Play Services版本时没有问题,但getMap()现已弃用(docs).

这是NPE的堆栈跟踪:

java.lang.NullPointerException
            at com.decos.fixi.fragments.FragmentLocationMap.initializeMap(FragmentLocationMap.java:132)
            at com.decos.fixi.fragments.FragmentLocationMap.onCreateView(FragmentLocationMap.java:95)
            at android.support.v4.app.Fragment.performCreateView(Fragment.java:1786)
            at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:947)
            at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1126)
            at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:739)
            at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1489)
            at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:454)
            at android.os.Handler.handleCallback(Handler.java:615)
            at android.os.Handler.dispatchMessage(Handler.java:92)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:4921)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1027)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:794)
            at dalvik.system.NativeStart.main(Native Method)