Question

关于这个问题已经有一些问题，但我找不到什么问题。我有一个带有ImageView和TextView的ListView。 listview使用item_layout.xlm，它包含两个元素。

我可以使用ArrayAdapter在ListView中填充TextView，但在尝试更改ImageView的源代码时出现NullPointerException。

 private void populateListViewLongFronde() {

        Cursor cursor = myDb.getAllDifEntries("long_fronde");
        ListView myList = (ListView) findViewById(R.id.listView);

        ArrayAdapter<String> arrayAdapter = new ArrayAdapter<String>(
                this,
                R.layout.item_layout,
                R.id.textView3,
                DBAdapter.AlResults );

        myList.setAdapter(arrayAdapter);

        ImageView myImage = (ImageView) findViewById(R.id.myImage);
        myImage.setImageResource(R.drawable.deltoide);

    }

这是Logcat：

09-15 02:38:50.319    1769-1769/? E/AndroidRuntime﹕ FATAL EXCEPTION: main
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.gobtron.database_test/com.gobtron.database_test.MainActivity}: java.lang.NullPointerException
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1956)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
            at android.app.ActivityThread.access$600(ActivityThread.java:123)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
            at android.os.Handler.dispatchMessage(Handler.java:99)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:4424)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
            at dalvik.system.NativeStart.main(Native Method)
     Caused by: java.lang.NullPointerException
            at com.gobtron.database_test.MainActivity.populateListViewLongFronde(MainActivity.java:119)
            at com.gobtron.database_test.MainActivity.onCreate(MainActivity.java:44)
            at android.app.Activity.performCreate(Activity.java:4466)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1920)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
            at android.app.ActivityThread.access$600(ActivityThread.java:123)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
            at android.os.Handler.dispatchMessage(Handler.java:99)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:4424)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
            at dalvik.system.NativeStart.main(Native Method)

Answer 1

您无法使用ArrayAdapter存储ImageView和TextView的数据。您需要实现自己的列表适配器，并且可能需要扩展BaseAdapter。您的代码可能会为您提供空指针，因为您无法通过在活动中使用findViewByID来访问列表视图元素，您无论如何都不应该这样做。

Answer 2

因为ImageView在item_layout.xml中，所以你应该这样做：

View view = LayoutInflater.from(activity).inflate(R.layout.item_layout, null);
    ImageView imgView=(ImageView)view.findViewById(R.id.myImage);

在填充ListView时更改ImageView源

2 个答案: