因此，在我的Android应用程序中，用户登录主要活动，然后他们继续主页活动并执行应用程序主要功能。此活动创建一个字符串列表，当用户单击注销按钮时，该列表将通过intent发送。在通过intent发送之前，我将列表转换为数组。然后在我的主要活动上有另一个按钮＆＃34;检索数据＆＃34;它启动了另一个活动，但它只是一个ListView。所以我想再次输入字符串数组来检索数据，这样用户就可以点击butoon并查看列表数据。 这是我从第一个发送字符串数组的地方：
btnLogout.setOnClickListener(new View.OnClickListener() {
public void onClick(View v)
{
String[] resultsArray = new String[userResults.size()];
Intent intentLogout=new Intent(getApplicationContext(),MainActivity.class);
intentLogout.putExtra("Results", resultsArray);
startActivity(intentLogout);
}
});
以下是我收到的信息并在我的主要活动中再次发送：
Bundle extras = getIntent().getExtras();
if(extras!=null)
{
results = extras.getStringArray("Results");
}
else
{
Toast.makeText(getApplicationContext(), "No data to retrieve yet", Toast.LENGTH_LONG).show();
}
btnRetrieveData.setOnClickListener(new View.OnClickListener() {
public void onClick(View v)
{
Intent intentRD=new Intent(getApplicationContext(),RetrieveDataActivity.class);
intentRD.putExtra("UserResults", results);
startActivity(intentRD);
}
});
这里是我的retrieveDataActivity，我之前没有使用过Listviews，所以我不确定我是否犯了任何明显/愚蠢的错误：
public class RetrieveDataActivity extends Activity
{
String [] values;
ListView listView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_listviewexampleactivity);
// Get ListView object
listView = (ListView) findViewById(R.id.list);
// Defined Array values to show in ListView
Bundle extras = getIntent().getExtras();
if(extras!=null)
{
values = extras.getStringArray("UserResults");
}
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1, android.R.id.text1, values);
// Assign adapter to ListView
listView.setAdapter(adapter);
// ListView Item Click Listener
listView.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,int position, long id)
{
// ListView Clicked item index
int itemPosition = position;
// ListView Clicked item value
String itemValue = (String) listView.getItemAtPosition(position);
// Show Alert
Toast.makeText(getApplicationContext(),"Position :"+itemPosition+" ListItem : " +itemValue , Toast.LENGTH_LONG) .show();
}
});
}
}
最后是logcat：
05-14 04:59:36.396: E/AndroidRuntime(28254): FATAL EXCEPTION: main
05-14 04:59:36.396: E/AndroidRuntime(28254): Process: com.gmail.Sheridjohn.letterchecker, PID: 28254
05-14 04:59:36.396: E/AndroidRuntime(28254): java.lang.NullPointerException
05-14 04:59:36.396: E/AndroidRuntime(28254): at android.widget.ArrayAdapter.createViewFromResource(ArrayAdapter.java:394)
05-14 04:59:36.396: E/AndroidRuntime(28254): at android.widget.ArrayAdapter.getView(ArrayAdapter.java:362)
05-14 04:59:36.396: E/AndroidRuntime(28254): at android.widget.AbsListView.obtainView(AbsListView.java:2263)
05-14 04:59:36.396: E/AndroidRuntime(28254): at android.widget.ListView.measureHeightOfChildren(ListView.java:1263)
05-14 04:59:36.396: E/AndroidRuntime(28254): at android.widget.ListView.onMeasure(ListView.java:1175)
05-14 04:59:36.396: E/AndroidRuntime(28254): at android.view.View.measure(View.java:16497)
05-14 04:59:36.396: E/AndroidRuntime(28254): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
05-14 04:59:36.396: E/AndroidRuntime(28254): at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
05-14 04:59:36.396: E/AndroidRuntime(28254): at android.view.View.measure(View.java:16497)
05-14 04:59:36.396: E/AndroidRuntime(28254): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
05-14 04:59:36.396: E/AndroidRuntime(28254): at com.android.internal.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:327)
05-14 04:59:36.396: E/AndroidRuntime(28254): at android.view.View.measure(View.java:16497)
05-14 04:59:36.396: E/AndroidRuntime(28254): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
05-14 04:59:36.396: E/AndroidRuntime(28254): at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
05-14 04:59:36.396: E/AndroidRuntime(28254): at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2291)
05-14 04:59:36.396: E/AndroidRuntime(28254): at android.view.View.measure(View.java:16497)
05-14 04:59:36.396: E/AndroidRuntime(28254): at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1916)
05-14 04:59:36.396: E/AndroidRuntime(28254): at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1113)
05-14 04:59:36.396: E/AndroidRuntime(28254): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1295)
05-14 04:59:36.396: E/AndroidRuntime(28254): at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1000)
05-14 04:59:36.396: E/AndroidRuntime(28254): at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5670)
05-14 04:59:36.396: E/AndroidRuntime(28254): at android.view.Choreographer$CallbackRecord.run(Choreographer.java:761)
05-14 04:59:36.396: E/AndroidRuntime(28254): at android.view.Choreographer.doCallbacks(Choreographer.java:574)
05-14 04:59:36.396: E/AndroidRuntime(28254): at android.view.Choreographer.doFrame(Choreographer.java:544)
05-14 04:59:36.396: E/AndroidRuntime(28254): at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:747)
05-14 04:59:36.396: E/AndroidRuntime(28254): at android.os.Handler.handleCallback(Handler.java:733)
05-14 04:59:36.396: E/AndroidRuntime(28254): at android.os.Handler.dispatchMessage(Handler.java:95)
05-14 04:59:36.396: E/AndroidRuntime(28254): at android.os.Looper.loop(Looper.java:136)
05-14 04:59:36.396: E/AndroidRuntime(28254): at android.app.ActivityThread.main(ActivityThread.java:5017)
05-14 04:59:36.396: E/AndroidRuntime(28254): at java.lang.reflect.Method.invokeNative(Native Method)
05-14 04:59:36.396: E/AndroidRuntime(28254): at java.lang.reflect.Method.invoke(Method.java:515)
05-14 04:59:36.396: E/AndroidRuntime(28254): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
05-14 04:59:36.396: E/AndroidRuntime(28254): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
05-14 04:59:36.396: E/AndroidRuntime(28254): at dalvik.system.NativeStart.main(Native Method)
答案 0 :(得分：1)
好的，问题是从意图
获取数组列表的位置尝试
Intent intent = new Intent(this, MainActivity.class);
values=extras.getStringArrayExtra("UserResults");
intent.putExtra("Arrays",values);
而不是
values = extras.getStringArray("UserResults");