如何从Android片段更新XML文本视图?
我正在尝试从如何从Android片段更新XML文本视图?,android,android-fragments,textview,Android,Android Fragments,Textview,我正在尝试从片段活动更新片段的文本视图。在else语句中,我首先创建一个片段,然后使用属于该片段的updateItemView()方法更新TextView,但我得到的只是一个 空指针异常 我可以通过if语句更新TextView,但是为什么我不能更新TextView 从else语句中 这是碎片活动的代码: public void toDeatailsBtn(View view){ ItemFragment listFragment = (ItemFragment) getSupportF
片段活动
更新片段的文本视图
。在else
语句中,我首先创建一个片段
,然后使用属于该片段的updateItemView()
方法更新TextView
,但我得到的只是一个
空指针异常
我可以通过if
语句更新TextView
,但是为什么我不能更新TextView
从else
语句中
这是碎片活动的代码
:
public void toDeatailsBtn(View view){
ItemFragment listFragment = (ItemFragment) getSupportFragmentManager()
.findFragmentById(R.id.large_layout_list_item_fragment);
if(listFragment != null){
//The "if" code is working.
listFragment.updateItemView();
}
// I'm swaping fragments here. I already added firstFragment to the
//fragment_container FrameLayout in other code.
else{
ItemFragment secondFragment = new ItemFragment();
FragmentTransaction transaction =
getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.fragment_container, secondFragment);
transaction.addToBackStack(null);
transaction.commit();
//This is giving me the null pointer exception, even though
//secondFragment has been created in theory.
secondFragment.updateItemView();
}
}
包含updateItemView()
方法的片段
:
public class ItemFragment extends Fragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
return inflater.inflate(R.layout.item_fragment, container, false);
}
public void updateItemView(){
TextView name = (TextView) getActivity()
.findViewById(R.id.list_item_fragment);
name.setText("TEST");
}
}
文本视图
:
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<TextView
android:id="@+id/list_item_fragment"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:freezesText="true" />
</LinearLayout>
</ScrollView>
错误日志:
01-06 00:59:08.425: E/AndroidRuntime(1610): java.lang.IllegalStateException: Could not execute method of the activity
01-06 00:59:08.425: E/AndroidRuntime(1610): at android.view.View$1.onClick(View.java:3591)
01-06 00:59:08.425: E/AndroidRuntime(1610): at android.view.View.performClick(View.java:4084)
01-06 00:59:08.425: E/AndroidRuntime(1610): at android.view.View$PerformClick.run(View.java:16966)
01-06 00:59:08.425: E/AndroidRuntime(1610): at android.os.Handler.handleCallback(Handler.java:615)
01-06 00:59:08.425: E/AndroidRuntime(1610): at android.os.Handler.dispatchMessage(Handler.java:92)
01-06 00:59:08.425: E/AndroidRuntime(1610): at android.os.Looper.loop(Looper.java:137)
01-06 00:59:08.425: E/AndroidRuntime(1610): at android.app.ActivityThread.main(ActivityThread.java:4745)
01-06 00:59:08.425: E/AndroidRuntime(1610): at java.lang.reflect.Method.invokeNative(Native Method)
01-06 00:59:08.425: E/AndroidRuntime(1610): at java.lang.reflect.Method.invoke(Method.java:511)
01-06 00:59:08.425: E/AndroidRuntime(1610): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
01-06 00:59:08.425: E/AndroidRuntime(1610): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
01-06 00:59:08.425: E/AndroidRuntime(1610): at dalvik.system.NativeStart.main(Native Method)
01-06 00:59:08.425: E/AndroidRuntime(1610): Caused by: java.lang.reflect.InvocationTargetException
01-06 00:59:08.425: E/AndroidRuntime(1610): at java.lang.reflect.Method.invokeNative(Native Method)
01-06 00:59:08.425: E/AndroidRuntime(1610): at java.lang.reflect.Method.invoke(Method.java:511)
01-06 00:59:08.425: E/AndroidRuntime(1610): at android.view.View$1.onClick(View.java:3586)
01-06 00:59:08.425: E/AndroidRuntime(1610): ... 11 more
01-06 00:59:08.425: E/AndroidRuntime(1610): Caused by: java.lang.NullPointerException
01-06 00:59:08.425: E/AndroidRuntime(1610): at com.site.myapp.ItemFragment.updateItemView(ItemFragment.java:27)
01-06 00:59:08.425: E/AndroidRuntime(1610): at com.site.myapp.MainFragmentActivity.toDetailsBtn(MainFragmentActivity.java:90)
01-06 00:59:08.425: E/AndroidRuntime(1610): ... 14 more
当您调用commit时,该片段事务不会立即完成,因此当您调用updateItemView()
时,无法立即找到TextView
。尝试使用强制进行交易:
//...
transaction.addToBackStack(null);
transaction.commit();
getSupportFragmentManager().executePendingTransaction();
secondFragment.updateItemView();
在myFragment
类中编写一个静态方法:
public static myFragment newInstance(String txt) {
myFragment myfragment = new myFragment();
Bundle args = new Bundle();
args.putString("TEXT", txt);
myfragment.setArguments(args);
return myfragment;
}
然后在OnCreate
方法的myFragment
类充气
tv.setText(getArguments().getString("TEXT"));
在mainFragmentActivity
class do中:
myFragment fragment = myFragment.newInstance(textToBeSent);
在更换之前
fragmentTransaction.replace(R.id.fr_dynamic, fragment);
fragmentTransaction.commit();
只是想知道为什么事务没有在commit()
@user1952398之后立即完成,这就是Fragment
系统是如何异步设计的。另外,您也可以从片段
的回调调用updateItemView
,而不是从外部调用,因为调用该方法更像是一个初始化过程。我不明白为什么你的问题会被否决,这是一个很好的问题,你也提供了相关的代码+stacktrace例外。
fragmentTransaction.replace(R.id.fr_dynamic, fragment);
fragmentTransaction.commit();