自定义listview的ArrayAdapter报空指针
====================问题描述====================
布局activity_list_view_test.xml
<LinearLayout 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:paddingBottom="@dimen/activity_vertical_margin" android:paddingLeft="@dimen/activity_horizontal_margin" android:paddingRight="@dimen/activity_horizontal_margin" android:paddingTop="@dimen/activity_vertical_margin" android:orientation="vertical" tools:context=".ListViewTest" > <TextView android:id="@+id/txtselection" android:layout_width="fill_parent" android:layout_height="wrap_content" > </TextView> <ListView android:id="@android:id/list" android:layout_width="wrap_content" android:layout_height="wrap_content" android:drawSelectorOnTop="false" android:orientation="vertical" > </ListView> </LinearLayout>
row list_vew_test_row.xml
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="horizontal" > <ImageView android:id="@+id/icon" android:layout_width="22dp" android:layout_height="wrap_content" android:paddingLeft="2dp" android:paddingRight="2dp" android:paddingTop="2dp" android:src="@drawable/ok" /> <TextView android:id="@+id/label" android:layout_width="wrap_content" android:layout_height="wrap_content" android:textSize="44sp" /> </LinearLayout>
java代码
public class ListViewTest extends ListActivity { TextView selection; String[] items = { "Apple", "orange", "Banana", "peach", "Grape", "Strawberry", "matermelon", "lemon" }; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_list_view_test); //setContentView(R.layout.list_vew_test_row); // setListAdapter(new ArrayAdapter<String>(this, // android.R.layout.simple_list_item_1, items)); setListAdapter(new IconicAdapter()); selection = (TextView)findViewById(R.id.txtselection); selection.setText("Please select"); } @Override public boolean onCreateOptionsMenu(Menu menu) { // Inflate the menu; this adds items to the action bar if it is present. getMenuInflater().inflate(R.menu.list_view_test, menu); return true; } public void onListItemClick(ListView parent, View v, int position, long id) { selection.setText(items[position]); } class IconicAdapter extends ArrayAdapter { IconicAdapter() { super(ListViewTest.this, R.layout.list_vew_test_row, items); } public View getView(int position, View convertView, ViewGroup parent) { LayoutInflater inflater = getLayoutInflater(); View row = inflater.inflate(R.layout.list_vew_test_row, parent, false); TextView label = (TextView)findViewById(R.id.label); label.setText(items[position]); ImageView icon = (ImageView)findViewById(R.id.icon); if (items[position].length() >= 5) { icon.setImageResource(R.drawable.ok); } else { icon.setImageResource(R.drawable.delete); } return row; } } }
error:
D/TextLayoutCache( 8977): Using debug level: 0 - Debug Enabled: 0 D/AndroidRuntime( 8977): Shutting down VM W/dalvikvm( 8977): threadid=1: thread exiting with uncaught exception (group=0x40aaf210) E/AndroidRuntime( 8977): FATAL EXCEPTION: main E/AndroidRuntime( 8977): java.lang.NullPointerException E/AndroidRuntime( 8977): at com.example.test.ListViewTest$IconicAdapter.getView(ListViewTest.java:58) E/AndroidRuntime( 8977): at android.widget.AbsListView.obtainView(AbsListView.java:2043) E/AndroidRuntime( 8977): at android.widget.ListView.measureHeightOfChildren(ListView.java:1244) E/AndroidRuntime( 8977): at android.widget.ListView.onMeasure(ListView.java:1155) E/AndroidRuntime( 8977): at android.view.View.measure(View.java:12897) E/AndroidRuntime( 8977): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4805) E/AndroidRuntime( 8977): at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1385) E/AndroidRuntime( 8977): at android.widget.LinearLayout.measureVertical(LinearLayout.java:676) E/AndroidRuntime( 8977): at android.widget.LinearLayout.onMeasure(LinearLayout.java:557) E/AndroidRuntime( 8977): at android.view.View.measure(View.java:12897) E/AndroidRuntime( 8977): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4805) E/AndroidRuntime( 8977): at android.widget.FrameLayout.onMeasure(FrameLayout.java:297) E/AndroidRuntime( 8977): at android.view.View.measure(View.java:12897) E/AndroidRuntime( 8977): at android.widget.LinearLayout.measureVertical(LinearLayout.java:828) E/AndroidRuntime( 8977): at android.widget.LinearLayout.onMeasure(LinearLayout.java:557) E/AndroidRuntime( 8977): at android.view.View.measure(View.java:12897) E/AndroidRuntime( 8977): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4805) E/AndroidRuntime( 8977): at android.widget.FrameLayout.onMeasure(FrameLayout.java:297) E/AndroidRuntime( 8977): at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2092) E/AndroidRuntime( 8977): at android.view.View.measure(View.java:12897) E/AndroidRuntime( 8977): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1064) E/AndroidRuntime( 8977): at android.view.ViewRootImpl.handleMessage(ViewRootImpl.java:2442) E/AndroidRuntime( 8977): at android.os.Handler.dispatchMessage(Handler.java:99) E/AndroidRuntime( 8977): at android.os.Looper.loop(Looper.java:137) E/AndroidRuntime( 8977): at android.app.ActivityThread.main(ActivityThread.java:4441) E/AndroidRuntime( 8977): at java.lang.reflect.Method.invokeNative(Native Method) E/AndroidRuntime( 8977): at java.lang.reflect.Method.invoke(Method.java:511) E/AndroidRuntime( 8977): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:823) E/AndroidRuntime( 8977): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:590) E/AndroidRuntime( 8977): at dalvik.system.NativeStart.main(Native Method) W/ActivityManager( 376): Force finishing activity com.example.test/.ListViewTest
58行:
label.setText(items[position]);
====================解决方案1====================
TextView label = (TextView)findViewById(R.id.label);把这句话改成TextView label = (TextView)row.findViewById(R.id.label);
因为这里要指定哪个页面的id。
====================解决方案2====================
TextView label = (TextView) row.findViewById(R.id.label); ImageView icon = (ImageView) row.findViewById(R.id.icon);