我的应用程序崩溃了。我有错误，我刚刚完成调试，因为标题说这就是问题所在。
调试时我发现导致问题的行：
listView.setAdapter(arrayAdapter2);
走向谷底。我在here之前有一个类似的nullpointerException。这次是不同的，因为我在正确的区域声明我的arrayadapter。在调试中，进入数组适配器的结果不是NULL。
我搜索了论坛，发现了这些：
Why am I getting an InvocationTargetException? Android 2D game
这些NullPointerExceptions在android中看起来很常见，但它们非常适合代码。
在阅读其他信息时，如果我错了，请更正我，如果arrayAdapter2为NULL，则null可以是唯一的位置。
public class ByZipcode extends Activity{
Button btngetLObyzipcode;
Spinner spinner1;
ProgressBar progressBar1;
EditText textinput4byzip;
UserFunctions userFunctions = new UserFunctions();
ArrayAdapter<String> arrayAdapter2;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.byzipcodepage);
arrayAdapter2 = new ArrayAdapter<String>(ByZipcode.this,android.R.layout.simple_list_item_1);
// Initializing spinner with predetermined results
spinner1 = (Spinner) findViewById(R.id.spinner1);
progressBar1 = (ProgressBar) findViewById(R.id.progressBar1);
textinput4byzip = (EditText) findViewById(R.id.textinput4byzip);
ArrayAdapter<CharSequence> spinnerAdapter = ArrayAdapter.createFromResource(this,
R.array.byzipspinner, android.R.layout.simple_spinner_item);
spinnerAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinner1.setAdapter(spinnerAdapter);
btngetLObyzipcode = (Button) findViewById(R.id.btngetLObyzipcode);
btngetLObyzipcode.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View arg0) {
if (textinput4byzip.getText() != null & textinput4byzip.getText().toString().length() == 5 ){
progressBar1.setVisibility(View.VISIBLE);
new DownloadDataTask().execute();
}
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.activity_main_screen, menu);
return true;
}
private class DownloadDataTask extends AsyncTask<JSONArray, JSONArray, ArrayList<String> > {
@Override
protected ArrayList<String> doInBackground(JSONArray... params) {
String spinValue = spinner1.getSelectedItem().toString();
//if(textinput4byzip.getText() != null)
JSONArray json = userFunctions.getCustomerbyZipCode((textinput4byzip.getText().toString()), spinValue);
ArrayList<String> customers = new ArrayList<String>();
for(int i=0; i < json.length() ; i++) {
JSONObject jarray;
try {
jarray = json.getJSONObject(i);
String zip = jarray.getString("CustomerName");
customers.add(zip);
Log.d(zip,"Output");
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
return customers;
}
protected void onPostExecute(ArrayList<String> result){
ListView listView = (ListView) findViewById(R.id.listView1);
arrayAdapter2.addAll(result);
listView.setAdapter(arrayAdapter2);
progressBar1.setVisibility(View.GONE);
Intent viewCustomers = new Intent(getApplicationContext(), StoreListView.class);
viewCustomers.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(viewCustomers);
}
}
}
如果您感兴趣，则失败如下：
02-10 17:39:36.976: E/AndroidRuntime(7686): FATAL EXCEPTION: main
02-10 17:39:36.976: E/AndroidRuntime(7686): java.lang.NullPointerException
02-10 17:39:36.976: E/AndroidRuntime(7686): at com.example.lo.ByZipcode$DownloadDataTask.onPostExecute(ByZipcode.java:93)
02-10 17:39:36.976: E/AndroidRuntime(7686): at com.example.lo.ByZipcode$DownloadDataTask.onPostExecute(ByZipcode.java:1)
02-10 17:39:36.976: E/AndroidRuntime(7686): at android.os.AsyncTask.finish(AsyncTask.java:631)
02-10 17:39:36.976: E/AndroidRuntime(7686): at android.os.AsyncTask.access$600(AsyncTask.java:177)
02-10 17:39:36.976: E/AndroidRuntime(7686): at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)
02-10 17:39:36.976: E/AndroidRuntime(7686): at android.os.Handler.dispatchMessage(Handler.java:99)
02-10 17:39:36.976: E/AndroidRuntime(7686): at android.os.Looper.loop(Looper.java:137)
02-10 17:39:36.976: E/AndroidRuntime(7686): at android.app.ActivityThread.main(ActivityThread.java:5039)
02-10 17:39:36.976: E/AndroidRuntime(7686): at java.lang.reflect.Method.invokeNative(Native Method)
02-10 17:39:36.976: E/AndroidRuntime(7686): at java.lang.reflect.Method.invoke(Method.java:511)
02-10 17:39:36.976: E/AndroidRuntime(7686): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
02-10 17:39:36.976: E/AndroidRuntime(7686): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
02-10 17:39:36.976: E/AndroidRuntime(7686): at dalvik.system.NativeStart.main(Native Method)
根据要求提供上述活动的xml页面：
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<EditText
android:id="@+id/textinput4byzip"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal|center_vertical"
android:contentDescription="@string/zipcodefielddescription"
android:ems="10"
android:gravity="center_vertical|center_horizontal"
android:inputType="number"
android:maxLength="@integer/zipcodelength"
android:textSize="@dimen/LargeFont" >
<requestFocus />
</EditText>
<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_vertical|center_horizontal"
android:text="@string/entrzip"
android:textAlignment="center"
android:textAppearance="?android:attr/textAppearanceLarge"
android:textSize="@dimen/MediumFont" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_gravity="center_vertical|center_horizontal"
android:orientation="vertical"
android:paddingLeft="@dimen/MediumFont"
android:paddingTop="@dimen/MediumFont" >
<ProgressBar
android:id="@+id/progressBar1"
style="?android:attr/progressBarStyleLarge"
android:layout_width="285dp"
android:layout_height="308dp"
android:layout_gravity="center_horizontal|center_vertical"
android:visibility="gone" />
<Spinner
android:id="@+id/spinner1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal|center_vertical"
android:entries="@array/byzipspinner"
android:textAlignment="center" />
<CheckBox
android:id="@+id/checkBox1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:checked="true"
android:text="@string/restaurants"
android:textSize="@dimen/LargeFont" />
<CheckBox
android:id="@+id/checkBox2"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:checked="true"
android:text="CheckBox"
android:textSize="@dimen/LargeFont" />
<CheckBox
android:id="@+id/checkBox3"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:checked="true"
android:text="CheckBox"
android:textSize="@dimen/LargeFont" />
<CheckBox
android:id="@+id/checkBox4"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:checked="true"
android:text="CheckBox"
android:textSize="@dimen/LargeFont" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center_vertical|center_horizontal"
android:orientation="vertical"
android:paddingRight="@dimen/MediumFont" >
<Button
android:id="@+id/btngetLObyzipcode"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/getlo"
android:textSize="@dimen/LargeFont" />
</LinearLayout>
</LinearLayout>
答案 0 :(得分：3)
ListView listView = (ListView) findViewById(R.id.listView1);
您正在byzipcodepage.xml查找标识为ListView的{{1}}。没有这样的观点;事实上，该布局中根本没有listView1。
如果您想要该视图中的列表（要使用适配器），您需要添加它;如果您的ListView处于不同的活动范围内，您可能需要稍微改变一下，以便将此活动的数据传递给该活动（可能通过ListView）。