Question

我知道这个问题一再被问到，但我无法做到这一点。

我只想将参数从Activity传递给Fragment。我已经尝试了我能在网上找到的所有东西，但我无法让它发挥作用。我总是得到NullPointerException错误。我甚至尝试过具有相同结果的测试代码。所以这就是：

MainActivity.java：

public class MainActivity extends Activity {

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

        Bundle bundle = new Bundle();
        bundle.putString("my_key", "My String");
        MyFragment myFrag = new MyFragment();
        myFrag.setArguments(bundle);
    }
}

MyFragment.java

public class MyFragment extends Fragment {

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragmentlayout, container, false);
        TextView text = (TextView) view.findViewById(R.id.game);
        String getArgument = getArguments().getString("my_key");
        text.setText(getArgument);
        return view;
    }
}

activity_main.xml中

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.test.test.MainActivity">

<fragment
    android:id="@+id/fragment_game"
    class="com.example.test.test.MyFragment"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="center"
    tools:layout="@layout/fragmentlayout" />

</FrameLayout>

fragmentlayout.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/fragment_game"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical"
tools:context=".MyFragment" >

    <TextView
        android:id="@+id/game"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textColor="#411124"
        />
</LinearLayout>

错误

FATAL EXCEPTION: main
                                                                     Process: com.example.test.test, PID: 11917
                                                                     java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.test.test/com.example.test.test.MainActivity}: android.view.InflateException: Binary XML file line #9: Binary XML file line #9: Error inflating class fragment
                                                                         at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2665)
                                                                         at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
                                                                         at android.app.ActivityThread.-wrap12(ActivityThread.java)
                                                                         at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
                                                                         at android.os.Handler.dispatchMessage(Handler.java:102)
                                                                         at android.os.Looper.loop(Looper.java:154)
                                                                         at android.app.ActivityThread.main(ActivityThread.java:6119)
                                                                         at java.lang.reflect.Method.invoke(Native Method)
                                                                         at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
                                                                         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
                                                                      Caused by: android.view.InflateException: Binary XML file line #9: Binary XML file line #9: Error inflating class fragment
                                                                      Caused by: android.view.InflateException: Binary XML file line #9: Error inflating class fragment
                                                                      Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.os.Bundle.getString(java.lang.String)' on a null object reference
                                                                         at com.example.test.test.MyFragment.onCreateView(MyFragment.java:20)
                                                                         at android.app.Fragment.performCreateView(Fragment.java:2353)
                                                                         at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:959)
                                                                         at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1149)
                                                                         at android.app.FragmentManagerImpl.addFragment(FragmentManager.java:1251)
                                                                         at android.app.FragmentManagerImpl.onCreateView(FragmentManager.java:2311)
                                                                         at android.app.FragmentController.onCreateView(FragmentController.java:98)
                                                                         at android.app.Activity.onCreateView(Activity.java:5901)
                                                                         at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:777)
                                                                         at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:727)
                                                                         at android.view.LayoutInflater.rInflate(LayoutInflater.java:858)
                                                                         at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:821)
                                                                         at android.view.LayoutInflater.inflate(LayoutInflater.java:518)
                                                                         at android.view.LayoutInflater.inflate(LayoutInflater.java:426)
                                                                         at android.view.LayoutInflater.inflate(LayoutInflater.java:377)
                                                                         at com.android.internal.policy.PhoneWindow.setContentView(PhoneWindow.java:412)
                                                                         at android.app.Activity.setContentView(Activity.java:2414)
                                                                         at com.example.test.test.MainActivity.onCreate(MainActivity.java:12)
                                                                         at android.app.Activity.performCreate(Activity.java:6679)
                                                                         at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118)
                                                                         at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2618)
                                                                         at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
                                                                         at android.app.ActivityThread.-wrap12(ActivityThread.java)
                                                                         at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
                                                                         at android.os.Handler.dispatchMessage(Handler.java:102)
                                                                         at android.os.Looper.loop(Looper.java:154)
                                                                         at android.app.ActivityThread.main(ActivityThread.java:6119)
                                                                         at java.lang.reflect.Method.invoke(Native Method)
                                                                         at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
                                                                         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)

如何在没有错误的情况下获取参数？

Answer 1

你收到错误，因为你把价值放在你的 bundle.putString（＆＃34; my_key＆＃34;，＆＃34; My String＆＃34;）; 并尝试从中获取日期 String getArgument = getArguments（）。getString（＆＃34; data＆＃34;）; 请确保哪个是您的关键my_key或数据？

Answer 2

你的代码有2个问题，a）你是以编程方式实例化Fragment，但你没有将它附加到Activity，所以它完全没用，并且b）你也在实例化xml布局中的Fragment，Fragment将无法在调用onCreateView之前设置参数。因此，如果您需要从xml中删除Fragment，请在Activity.onCreate中创建一个实例，设置参数，然后将其附加到Activity FragmentManager

将activity_main.xml更改为此（请注意android:id属性）

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/fragment_container"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.test.test.MainActivity">    

</FrameLayout>

和onCreate的{{1}}

MainActivity

getArgument（）始终为null

2 个答案: