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当我尝试访问包含我所有保存的数据（在文件中）的列表视图时，我正面临一个 FC，这里是 logcat：

03-20 22:43:33.686: ERROR/AndroidRuntime(5315): FATAL EXCEPTION: main
03-20 22:43:33.686: ERROR/AndroidRuntime(5315): java.lang.NullPointerException
03-20 22:43:33.686: ERROR/AndroidRuntime(5315):     at android.widget.ArrayAdapter.createViewFromResource(ArrayAdapter.java:355)
03-20 22:43:33.686: ERROR/AndroidRuntime(5315):     at android.widget.ArrayAdapter.getView(ArrayAdapter.java:323)
03-20 22:43:33.686: ERROR/AndroidRuntime(5315):     at android.widget.AbsListView.obtainView(AbsListView.java:1430)
03-20 22:43:33.686: ERROR/AndroidRuntime(5315):     at android.widget.ListView.makeAndAddView(ListView.java:1745)
03-20 22:43:33.686: ERROR/AndroidRuntime(5315):     at android.widget.ListView.fillDown(ListView.java:670)
03-20 22:43:33.686: ERROR/AndroidRuntime(5315):     at android.widget.ListView.fillFromTop(ListView.java:727)
03-20 22:43:33.686: ERROR/AndroidRuntime(5315):     at android.widget.ListView.layoutChildren(ListView.java:1598)
03-20 22:43:33.686: ERROR/AndroidRuntime(5315):     at android.widget.AbsListView.onLayout(AbsListView.java:1260)
03-20 22:43:33.686: ERROR/AndroidRuntime(5315):     at android.view.View.layout(View.java:7175)
03-20 22:43:33.686: ERROR/AndroidRuntime(5315):     at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1254)
03-20 22:43:33.686: ERROR/AndroidRuntime(5315):     at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1130)
03-20 22:43:33.686: ERROR/AndroidRuntime(5315):     at android.widget.LinearLayout.onLayout(LinearLayout.java:1047)
03-20 22:43:33.686: ERROR/AndroidRuntime(5315):     at android.view.View.layout(View.java:7175)
03-20 22:43:33.686: ERROR/AndroidRuntime(5315):     at android.widget.FrameLayout.onLayout(FrameLayout.java:338)
03-20 22:43:33.686: ERROR/AndroidRuntime(5315):     at android.view.View.layout(View.java:7175)
03-20 22:43:33.686: ERROR/AndroidRuntime(5315):     at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1254)
03-20 22:43:33.686: ERROR/AndroidRuntime(5315):     at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1130)
03-20 22:43:33.686: ERROR/AndroidRuntime(5315):     at android.widget.LinearLayout.onLayout(LinearLayout.java:1047)
03-20 22:43:33.686: ERROR/AndroidRuntime(5315):     at android.view.View.layout(View.java:7175)
03-20 22:43:33.686: ERROR/AndroidRuntime(5315):     at android.widget.FrameLayout.onLayout(FrameLayout.java:338)
03-20 22:43:33.686: ERROR/AndroidRuntime(5315):     at android.view.View.layout(View.java:7175)
03-20 22:43:33.686: ERROR/AndroidRuntime(5315):     at android.view.ViewRoot.performTraversals(ViewRoot.java:1140)
03-20 22:43:33.686: ERROR/AndroidRuntime(5315):     at android.view.ViewRoot.handleMessage(ViewRoot.java:1859)
03-20 22:43:33.686: ERROR/AndroidRuntime(5315):     at android.os.Handler.dispatchMessage(Handler.java:99)
03-20 22:43:33.686: ERROR/AndroidRuntime(5315):     at android.os.Looper.loop(Looper.java:123)
03-20 22:43:33.686: ERROR/AndroidRuntime(5315):     at android.app.ActivityThread.main(ActivityThread.java:3683)
03-20 22:43:33.686: ERROR/AndroidRuntime(5315):     at java.lang.reflect.Method.invokeNative(Native Method)
03-20 22:43:33.686: ERROR/AndroidRuntime(5315):     at java.lang.reflect.Method.invoke(Method.java:507)
03-20 22:43:33.686: ERROR/AndroidRuntime(5315):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
03-20 22:43:33.686: ERROR/AndroidRuntime(5315):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
03-20 22:43:33.686: ERROR/AndroidRuntime(5315):     at dalvik.system.NativeStart.main(Native Method)

list_item.xml：

<?xml version="1.0" encoding="utf-8"?>

 <TextView xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:padding="10dp"
    android:textSize="13sp" >
</TextView>

histo.xml：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="fill_parent"
    android:layout_height="fill_parent" android:layout_weight="1"
    android:id="@+id/ViewHisto">
    <ListView android:id="@+id/lv" android:layout_width="fill_parent"
        android:layout_height="fill_parent" android:layout_weight="1" />
</LinearLayout>

访问 ListView 的函数：

public void updatelv(Activity activity) {
        SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(context);
        String fileName = getResources().getString(R.string.fileName);
        fileDir = "" + preferences.getString("login", "") + "."+ preferences.getString("marque", "") + ".";
        s = myIO.ReadFilePerLine(getApplicationContext(), fileDir+fileName);
            updatelv(this);
        ListView L = (ListView) findViewById(R.id.lv);
        L.setAdapter(new ArrayAdapter<String>(this, R.layout.list_item, s));
        }

创建函数：

public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.histo);
        context = getApplicationContext();
        activity = this;
        final SharedPreferences preferences = PreferenceManager
                .getDefaultSharedPreferences(context);
        String fileName = getResources().getString(R.string.fileName);
        fileDir = "" + preferences.getString("login", "") + "."+ preferences.getString("marque", "") + ".";
        s = myIO.ReadFilePerLine(getApplicationContext(), fileDir + fileName);
        updatelv(this);
        ListView L = (ListView) findViewById(R.id.lv);
        L.setTextFilterEnabled(true);
.........

这究竟意味着什么？这是一个 XML 问题吗？谢谢 ：）。

4

3 回答 3

1

您的 TextView 缺少 id。你需要给它一个像

android:id="@+id/text"

并像这样创建 ArrayAdapter

L.setAdapter(new ArrayAdapter<String>(this, R.id.text, s));

该 ArrayAdapter 构造函数期望资源是 TextView 的 id，而不是布局。因此，使用您当前的代码，在 ArrayAdapter 中它正在执行类似的操作

TextView tv = (TextView) findViewById(R.layout.list_item);

并且 tv 为空，因为它不是布局。

于 2011-03-20T23:40:42.873 回答
0

您可以在此处查找 android 源代码中的相应行。

如果您正在为不同的版本构建它可能会有所不同，但对于 2.3.3 这意味着它在尝试设置相应 TextView 的文本时返回 NPE：

354  } else {
355  text.setText(item.toString());
356  }

可能与 xml 相关，尽管 AFAIK 唯一的错误是在编译时标记的。ListView 在你膨胀之后和 ArrayAdapter 尝试编辑它之前是否有效？

于 2011-03-20T23:34:57.437 回答
0

我遇到了同样的错误，在我的情况下，ArrayAdapter 创建列表所需的对象数组没有正确填充。因此，当 Android 试图用数组中的数据填充 ListView 并且数组中的一个对象为 null 时，就会引发异常。因此，请确保您传递给 ArrayAdapter 的“s”被正确创建并且不包含任何“损坏”数据。

于 2011-08-24T21:21:54.653 回答