Java listview中arrayadapter的空指针异常。安卓
我有一个主视图（listview）和第二个主视图（edittext）。我使用startActivityforResult（）将数据从第二个主视图向后传递到第一个主视图。我已经测试过了，我收到的字符串没有问题。但是，在listview上显示它时存在一些问题。我的listview有两个xml文件，一个用于listview布局，另一个用于textview行。我不知道为什么会出现空指针异常Java listview中arrayadapter的空指针异常。安卓,java,android,arrays,listview,nullpointerexception,Java,Android,Arrays,Listview,Nullpointerexception,我有一个主视图（listview）和第二个主视图（edittext）。我使用startActivityforResult（）将数据从第二个主视图向后传递到第一个主视图。我已经测试过了，我收到的字符串没有问题。但是，在listview上显示它时存在一些问题。我的listview有两个xml文件，一个用于listview布局，另一个用于textview行。我不知道为什么会出现空指针异常 03-14 22:50:33.429 9268-9268/com.example.anusha.app E/
03-14 22:50:33.429 9268-9268/com.example.anusha.app E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.example.anusha.app, PID: 9268
java.lang.NullPointerException
at android.widget.ArrayAdapter.createViewFromResource(ArrayAdapter.java:392)
at android.widget.ArrayAdapter.getView(ArrayAdapter.java:362)
at android.widget.AbsListView.obtainView(AbsListView.java:2780)
at android.widget.ListView.measureHeightOfChildren(ListView.java:1274)
at android.widget.ListView.onMeasure(ListView.java:1186)
at android.view.View.measure(View.java:17594)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5398)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1410)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:695)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:588)
at android.view.View.measure(View.java:17594)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5398)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
at android.view.View.measure(View.java:17594)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5398)
at android.support.v7.internal.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:453)
at android.view.View.measure(View.java:17594)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5398)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
at android.view.View.measure(View.java:17594)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5398)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1410)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:695)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:588)
at android.view.View.measure(View.java:17594)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5398)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2588)
at android.view.View.measure(View.java:17594)
at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2308)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2030)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1267)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6640)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:813)
at android.view.Choreographer.doCallbacks(Choreographer.java:613)
at android.view.Choreographer.doFrame(Choreographer.java:583)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:799)
at android.os.Handler.handleCallback(Handler.java:733)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:146)
at android.app.ActivityThread.main(ActivityThread.java:5635)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1291)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1107)
at dalvik.system.NativeStart.main(Native Method)
ArrayList<String> array= new ArrayList<>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_address_list);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
ArrayAdapter<String> adapter = new ArrayAdapter<>(this, R.layout.activity_address_list,R.id.rowTextView, array);
ListView listview = (ListView) findViewById(R.id.listView);
listview.setAdapter(adapter);
}
private void Add() {
Intent intent = new Intent(AddressList.this, SilentGeofence.class);
startActivityForResult(intent, 2);
}
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (requestCode == 2) {
if (resultCode == RESULT_OK){
String result = data.getStringExtra("result");
array.add(result);
}
}
}
必须在
getSupportActionBar（）之后的onCreate（）
中初始化列表。setDisplayHomeAsUpEnabled（true）
而且您的ArrayAdapter
应该是一个字段而不是局部变量，因为在执行array.add（result）
之后，您还必须调用adapter.notifyDataSetChanged（）
，以便刷新和填充listview公共ArrayAdapter（上下文，int-resource，int-textViewResourceId，T[]（对象）
在API级别1中添加
建造师
参数
上下文当前上下文。
resource—包含要在实例化视图时使用的布局的布局文件的资源ID。
textViewResourceId要填充的布局资源中的TextView的id
对象要在ListView中表示的对象
因此，您应该使用textview的布局，而不是listview布局，请参见此处
new ArrayAdapter（此为R.layout.layout\u包含R.id.rowTextView、R.id.rowTextView、数组的xml\u的名称）；
数组中未填充项目。在哪里调用Add（）？您的问题是ArrayAdapter adapter=new ArrayAdapter（这是R.layout.activity\u address\u list，R.id.rowTextView，array）。阅读文档，了解如何填充arrayAdapter
i call Add（）onOptionsItemSelected（），这是我的条形按钮项目之一@RaghunandanI正在使用公共ArrayAdapter（上下文上下文上下文，int资源，int textViewResourceId，T[]对象）@ShayanPourvatan数组正在从第二个main获取项目并在onActivityResult（）中更新，对吗？不起作用。我将数组适配器设置为字段变量，并将Adapter.notifyDataSetChanged（）放在Array.add（result）之后，应用程序仍然崩溃@Ishan Khannait崩溃，原因是：onCreate（）之前的活动无法使用系统服务@Ishan khanna
Button add = (Button) findViewById(R.id.button);
add.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
String ag = txt1.getText().toString().trim();
txt1.setText("");
Intent returnIntent = new Intent();
returnIntent.putExtra("result",ag);
setResult(RESULT_OK,returnIntent);
finish();
new ArrayAdapter<>(this, R.layout.layout_name_of_the_xml_containing_textview,R.id.rowTextView, array);