Question

我正在尝试设置数组适配器并具有以下代码：

private String[] mServices;
private ListView mDrawerList;
//Ends Here

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

    //For Navigation Drawer
    mServices = getResources().getStringArray(R.array.drawer_services);
    mDrawerList = (ListView) findViewById (R.id.left_drawer);

    mDrawerList.setAdapter(new ArrayAdapter<String>(this, R.layout.drawer_list_item, mServices));

我尝试设置Adapter的最后一行代码，我得到一个NullPointerException。如果我尝试导航到包含此代码的页面，应用程序将崩溃。

任何指针？

这是调试：

07-08 20:05:22.885: E/AndroidRuntime(2351): FATAL EXCEPTION: main 07-08 20:05:22.885: E/AndroidRuntime(2351): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.parrot.urlripper/com.parrot.urlripper.google}: java.lang.NullPointerException 07-08 20:05:22.885: E/AndroidRuntime(2351): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647) 07-08 20:05:22.885: E/AndroidRuntime(2351): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663) 07-08 20:05:22.885: E/AndroidRuntime(2351): at android.app.ActivityThread.access$1500(ActivityThread.java:117) 07-08 20:05:22.885: E/AndroidRuntime(2351): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931) 07-08 20:05:22.885: E/AndroidRuntime(2351): at android.os.Handler.dispatchMessage(Handler.java:99) 07-08 20:05:22.885: E/AndroidRuntime(2351): at android.os.Looper.loop(Looper.java:123) 07-08 20:05:22.885: E/AndroidRuntime(2351): at android.app.ActivityThread.main(ActivityThread.java:3683) 07-08 20:05:22.885: E/AndroidRuntime(2351): at java.lang.reflect.Method.invokeNative(Native Method) 07-08 20:05:22.885: E/AndroidRuntime(2351): at java.lang.reflect.Method.invoke(Method.java:507) 07-08 20:05:22.885: E/AndroidRuntime(2351): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839) 07-08 20:05:22.885: E/AndroidRuntime(2351): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597) 07-08 20:05:22.885: E/AndroidRuntime(2351): at dalvik.system.NativeStart.main(Native Method) 07-08 20:05:22.885: E/AndroidRuntime(2351): Caused by: java.lang.NullPointerException 07-08 20:05:22.885: E/AndroidRuntime(2351): at com.parrot.urlripper.google.onCreate(google.java:35) 07-08 20:05:22.885: E/AndroidRuntime(2351): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047) 07-08 20:05:22.885: E/AndroidRuntime(2351): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)

Answer 1

在ArrayAdapter的构造函数中，您必须按照Android文档中的描述传递TextView标识： ArrayAdapter

互联网上有一些关于这个主题的教程，例如这个：ArrayAdapter basic tutorial

您的问题也可能来自mServices，可以为空。

编辑：

以下代码适用于我：

活动：

public class MainActivity extends Activity {

    private String[] mServices = new String[] {"Test1", "Test2", "Test3", "Test4"};
    private ListView mDrawerList;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mDrawerList = (ListView) findViewById(R.id.left_drawer);
        mDrawerList.setAdapter(new ArrayAdapter<String>(this, R.layout.text_view, mServices));
    }
}

activity_main.xml文件：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <ListView
        android:id="@+id/left_drawer"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:drawSelectorOnTop="false"
        android:choiceMode="multipleChoice"
    />
</LinearLayout>

和text_view.xml文件：

<TextView xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="15dp"
    android:textColor="@android:color/black"
    android:textStyle="italic">
</TextView>

Answer 2

你试过这条线吗？

mDrawerList.setAdapter（new ArrayAdapter（this，R.layout.drawer_list_item，{“test”，“test”，“test”}））;

如果这解决了你的问题，那么mServices数组就是问题..

使用setAdapter的NullPointerException - 尝试设置数组适配器

2 个答案: