Question

我已经创建了一个自定义适配器，将图像放在我的listView中，但在textView.setText（text）中给了我一个空指针异常。

这是我的适配器异常的部分：

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {

        LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);

        View rowView = inflater.inflate(rowResourceId, parent, false);
        ImageView imageView = (ImageView) rowView.findViewById(R.id.imageFileView);
        TextView textView = (TextView) rowView.findViewById(R.id.fileName);

        int pos = position+4;

        String name = Names[pos];

        String extFile = Names[pos].substring(Names[pos].lastIndexOf(".")+1);

        String uri = "drawable/"+extFile+".png";

        textView.setText(name);     

        Uri imgUri=Uri.parse(uri);
        imageView.setImageURI(imgUri);
        return rowView;  
    }

当我有异常时，这是我的LogCat：

06-14 12:15:04.616: E/AndroidRuntime(678): FATAL EXCEPTION: main
06-14 12:15:04.616: E/AndroidRuntime(678): java.lang.NullPointerException
06-14 12:15:04.616: E/AndroidRuntime(678):  at com.example.poc_cubbyhole.ItemAdapter.getView(ItemAdapter.java:59)
06-14 12:15:04.616: E/AndroidRuntime(678):  at android.widget.HeaderViewListAdapter.getView(HeaderViewListAdapter.java:220)
06-14 12:15:04.616: E/AndroidRuntime(678):  at android.widget.AbsListView.obtainView(AbsListView.java:1430)
06-14 12:15:04.616: E/AndroidRuntime(678):  at android.widget.ListView.makeAndAddView(ListView.java:1745)
06-14 12:15:04.616: E/AndroidRuntime(678):  at android.widget.ListView.fillSpecific(ListView.java:1290)
06-14 12:15:04.616: E/AndroidRuntime(678):  at android.widget.ListView.layoutChildren(ListView.java:1588)
06-14 12:15:04.616: E/AndroidRuntime(678):  at android.widget.AbsListView.onLayout(AbsListView.java:1260)
06-14 12:15:04.616: E/AndroidRuntime(678):  at android.view.View.layout(View.java:7175)
06-14 12:15:04.616: E/AndroidRuntime(678):  at android.widget.RelativeLayout.onLayout(RelativeLayout.java:912)
06-14 12:15:04.616: E/AndroidRuntime(678):  at android.view.View.layout(View.java:7175)
06-14 12:15:04.616: E/AndroidRuntime(678):  at android.widget.FrameLayout.onLayout(FrameLayout.java:338)
06-14 12:15:04.616: E/AndroidRuntime(678):  at android.view.View.layout(View.java:7175)
06-14 12:15:04.616: E/AndroidRuntime(678):  at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1254)
06-14 12:15:04.616: E/AndroidRuntime(678):  at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1130)
06-14 12:15:04.616: E/AndroidRuntime(678):  at android.widget.LinearLayout.onLayout(LinearLayout.java:1047)
06-14 12:15:04.616: E/AndroidRuntime(678):  at android.view.View.layout(View.java:7175)
06-14 12:15:04.616: E/AndroidRuntime(678):  at android.widget.FrameLayout.onLayout(FrameLayout.java:338)
06-14 12:15:04.616: E/AndroidRuntime(678):  at android.view.View.layout(View.java:7175)
06-14 12:15:04.616: E/AndroidRuntime(678):  at android.view.ViewRoot.performTraversals(ViewRoot.java:1140)
06-14 12:15:04.616: E/AndroidRuntime(678):  at android.view.ViewRoot.handleMessage(ViewRoot.java:1859)
06-14 12:15:04.616: E/AndroidRuntime(678):  at android.os.Handler.dispatchMessage(Handler.java:99)
06-14 12:15:04.616: E/AndroidRuntime(678):  at android.os.Looper.loop(Looper.java:123)
06-14 12:15:04.616: E/AndroidRuntime(678):  at android.app.ActivityThread.main(ActivityThread.java:3683)
06-14 12:15:04.616: E/AndroidRuntime(678):  at java.lang.reflect.Method.invokeNative(Native Method)
06-14 12:15:04.616: E/AndroidRuntime(678):  at java.lang.reflect.Method.invoke(Method.java:507)
06-14 12:15:04.616: E/AndroidRuntime(678):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
06-14 12:15:04.616: E/AndroidRuntime(678):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
06-14 12:15:04.616: E/AndroidRuntime(678):  at dalvik.system.NativeStart.main(Native Method)

这是在我的listView中创建项目的xml文件：

<ImageView
            android:id="@+id/imageFileView"
            android:layout_width="32dp"
            android:layout_height="32dp"
            android:layout_alignParentLeft="true"
            android:layout_marginLeft="9dp"
            android:layout_alignParentTop="true"/>
    <TextView
            android:layout_alignBottom="@+id/fileName"
            android:layout_width="97dp"
            android:layout_height="32dp"
            android:id="@+id/textView"
            android:layout_alignParentLeft="true"
            android:layout_marginLeft="66dp"
            android:layout_alignParentRight="true"
            android:gravity="center_vertical"/>

这是我的listView：

<com.example.poc_cubbyhole.widgets.PullToRefreshListView
    android:id="@+id/list_files"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_above="@+id/button_upload"
    android:layout_alignParentTop="true" 
    />

我使用小部件更改添加拉动和刷新到我的listView

Answer 1

更改此

TextView textView = (TextView) rowView.findViewById(R.id.fileName);

到

TextView textView = (TextView) rowView.findViewById(R.id.textView);

在您的getView方法中，因为您的TextView ID为textView而不是fileName

Answer 2

你可以从阵列上的位置得到空值：

        int pos = position+4;

        String name = Names[pos];

对于中级解决方案，您可以添加以下内容：

int pos = position+4;

String name = ""+Names[pos];

所以你没有空值而且没有得到nullpointer。

现在，如果你想要获得nul值的正确解决方案，那么每次执行时都要调试应用程序并检查数组和名称的价值。祝你好运..

Answer 3

即使我的View ID正确，我也遇到了问题。但最后我更改了id并清理了项目然后构建了一次。它工作正常。

android textView.setText（）给我空指针异常

3 个答案: