Question

我一直都在寻找答案，但这里或其他地方发布的一般答案都没有帮助。我试图通过我的Activity的onCreate函数中的代码设置TextView的文本，但它只是不起作用。

这是活动代码（编辑：嵌套片段代码）：

import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v7.app.ActionBarActivity;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

public class NationalActivity extends ActionBarActivity {

private String nationID;
public static final String REVENUE_MESSAGE = "com.murrow.natlrevcalc.REVENUE";
private int revenue;


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

    if (savedInstanceState == null) {
        getSupportFragmentManager().beginTransaction()
                .add(R.id.container, new NationalFragment()).commit();
    }

    Intent i = getIntent();
    nationID = i.getStringExtra(RunNationalsActivity.NATION);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {

    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.national, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();
    if (id == R.id.action_settings) {
        return true;
    }
    return super.onOptionsItemSelected(item);
}

/**
 * National Fragment
 */
public static class NationalFragment extends Fragment {

    public NationalFragment() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_national,
                container, false);

        TextView test = (TextView)getView().findViewById(R.id.townText);
        test.setText("This is not working");

        return rootView;


    }
}

}

活动XML：

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.murrow.natlrevcalc.NationalActivity"
tools:ignore="MergeRootFrame" >

<RelativeLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

</RelativeLayout>

片段（所有信息都是）XML：

<TableLayout 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"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".NationalActivity$NationalFragment" >

<ScrollView
    android:layout_width="fill_parent"
    android:layout_height="wrap_content" >

    <TableLayout
        android:id="@+id/nationalLayout"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="vertical" >

        <TextView
            android:id="@+id/townText"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Towns"
            android:textAppearance="?android:attr/textAppearanceMedium" />

        <EditText
            android:id="@+id/yellowTown"
            android:layout_width="52dp"
            android:layout_height="wrap_content"
            android:ems="10"
            android:inputType="number" />

        <EditText
            android:id="@+id/greenTown"
            android:layout_width="52dp"
            android:layout_height="wrap_content"
            android:ems="10"
            android:inputType="number" />

        <EditText
            android:id="@+id/brownTown"
            android:layout_width="52dp"
            android:layout_height="wrap_content"
            android:ems="10"
            android:inputType="number" />

        <android.support.v7.widget.Space
            android:layout_width="wrap_content"
            android:layout_height="wrap_content" />

        <TextView
            android:id="@+id/textView2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Cities"
            android:textAppearance="?android:attr/textAppearanceMedium" />

        <EditText
            android:id="@+id/yellowCity"
            android:layout_width="52dp"
            android:layout_height="wrap_content"
            android:ems="10"
            android:inputType="number" />

        <EditText
            android:id="@+id/greenCity"
            android:layout_width="52dp"
            android:layout_height="wrap_content"
            android:ems="10"
            android:inputType="number" />

        <EditText
            android:id="@+id/brownCity"
            android:layout_width="52dp"
            android:layout_height="wrap_content"
            android:ems="10"
            android:inputType="number" />

        <EditText
            android:id="@+id/greyCity"
            android:layout_width="52dp"
            android:layout_height="wrap_content"
            android:ems="10"
            android:inputType="number" />

        <TextView
            android:id="@+id/TextView01"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="GC"
            android:textAppearance="?android:attr/textAppearanceMedium" />

        <EditText
            android:id="@+id/yellowGC"
            android:layout_width="52dp"
            android:layout_height="wrap_content"
            android:ems="10"
            android:inputType="number" />

        <EditText
            android:id="@+id/greenGC"
            android:layout_width="52dp"
            android:layout_height="wrap_content"
            android:ems="10"
            android:inputType="number" />

        <EditText
            android:id="@+id/brownGC"
            android:layout_width="52dp"
            android:layout_height="wrap_content"
            android:ems="10"
            android:inputType="number" />

        <EditText
            android:id="@+id/greyGC"
            android:layout_width="52dp"
            android:layout_height="wrap_content"
            android:ems="10"
            android:inputType="number" />

        <TextView
            android:id="@+id/TextView02"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Met"
            android:textAppearance="?android:attr/textAppearanceMedium" />

        <EditText
            android:id="@+id/yellowMet"
            android:layout_width="52dp"
            android:layout_height="wrap_content"
            android:ems="10"
            android:inputType="number" />

        <EditText
            android:id="@+id/greenMet"
            android:layout_width="52dp"
            android:layout_height="wrap_content"
            android:ems="10"
            android:inputType="number" />

        <EditText
            android:id="@+id/brownMet"
            android:layout_width="52dp"
            android:layout_height="wrap_content"
            android:ems="10"
            android:inputType="number" />

        <EditText
            android:id="@+id/greyMet"
            android:layout_width="52dp"
            android:layout_height="wrap_content"
            android:ems="10"
            android:inputType="number" />

        <TextView
            android:id="@+id/textView4"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textAppearance="?android:attr/textAppearanceLarge" />

        <Button
            android:id="@+id/run"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:onClick="run"
            android:text="Run" />
    </TableLayout>
</ScrollView>

更具体地说，问题是TextView：

<TextView
            android:id="@+id/townText"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Towns"
            android:textAppearance="?android:attr/textAppearanceMedium" />

编辑：LogCat错误：

04-23 09:50:18.881: E/AndroidRuntime(14665): FATAL EXCEPTION: main
04-23 09:50:18.881: E/AndroidRuntime(14665): java.lang.RuntimeException: Unable to   start activity 

    ComponentInfo{com.murrow.natlrevcalc/com.murrow.natlrevcalc.NationalActivity}: java.lang.NullPointerException
04-23 09:50:18.881: E/AndroidRuntime(14665):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2295)
04-23 09:50:18.881: E/AndroidRuntime(14665):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2349)
04-23 09:50:18.881: E/AndroidRuntime(14665):    at android.app.ActivityThread.access$700(ActivityThread.java:159)
04-23 09:50:18.881: E/AndroidRuntime(14665):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1316)
04-23 09:50:18.881: E/AndroidRuntime(14665):    at android.os.Handler.dispatchMessage(Handler.java:99)
04-23 09:50:18.881: E/AndroidRuntime(14665):    at android.os.Looper.loop(Looper.java:137)
04-23 09:50:18.881: E/AndroidRuntime(14665):    at android.app.ActivityThread.main(ActivityThread.java:5419)
04-23 09:50:18.881: E/AndroidRuntime(14665):    at java.lang.reflect.Method.invokeNative(Native Method)
04-23 09:50:18.881: E/AndroidRuntime(14665):    at java.lang.reflect.Method.invoke(Method.java:525)
04-23 09:50:18.881: E/AndroidRuntime(14665):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1187)
04-23 09:50:18.881: E/AndroidRuntime(14665):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1003)
04-23 09:50:18.881: E/AndroidRuntime(14665):    at dalvik.system.NativeStart.main(Native Method)
04-23 09:50:18.881: E/AndroidRuntime(14665): Caused by: java.lang.NullPointerException
04-23 09:50:18.881: E/AndroidRuntime(14665):    at com.murrow.natlrevcalc.NationalActivity.onCreate(NationalActivity.java:95)
04-23 09:50:18.881: E/AndroidRuntime(14665):    at android.app.Activity.performCreate(Activity.java:5372)
04-23 09:50:18.881: E/AndroidRuntime(14665):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1104)
04-23 09:50:18.881: E/AndroidRuntime(14665):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2257)
04-23 09:50:18.881: E/AndroidRuntime(14665):    ... 11 more

我尝试过使用Handler，我尝试使用/搞乱线程。我已经尝试过一些建议，这些建议在我在本网站的其他帖子中找不到任何意义。

活动/片段关系应该没问题，因为活动会使片段膨胀（据我所知）。

请帮忙！

感谢。

Answer 1

townText属于Fragment View的层次结构。您应该在Fragment子类中查找它。在我看来，最好的地方是onViewCreated回调，但您可以在getView().findViewById返回后使用onCreateView

Answer 2

您需要将textview代码放在方法OnCreateView() @ NationalFragment

中

public class NationalFragment extends Fragment {

  private OnItemSelectedListener listener;

  @Override
  public View onCreateView(LayoutInflater inflater, ViewGroup container,
      Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.activity_national,
        container, false);

TextView test = (TextView)view.findViewById(R.id.townText);
    test.setText("This is not working");

    return view;
  }

}

Android textView.setText（）崩溃的应用程序

2 个答案: