请帮我解决这个问题，因为我在网上搜索了解决方案而没有获得解决方案。
我要做的是从警告对话框中获取数据，然后单击确定按钮。 单击TypeActivity上的项后会弹出警告对话框。此单击的结果将传递给HomeActivity，其中警告对话框将弹出一个文本字段。 但是每次我输入文本字段并按下＆＃34; OK＆＃34;按钮，应用程序崩溃。 logcat显示空指针异常。我也会显示logcat内容。谢谢你的帮助。
我的代码如下
TypeActivity：
String[] typeTag = {"TypeA","TypeB","TypeC","TypeD"};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setListAdapter(new MyAdapter(TypeActivity.this,R.layout.spinnerrow, typeTag));
getListView().setAdapter(new MyAdapter(TypeActivity.this,R.layout.spinnerrow, typeTag));
getListView().setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Intent returnIntent = new Intent();
returnIntent.putExtra("selectedType", typeTag[position]);
setResult(RESULT_OK, returnIntent);
finish();
}
});
HomeActivity：
@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if(requestCode == 1 && resultCode == RESULT_OK){
String temp = data.getStringExtra("selectedType");
AlertDialog.Builder builder2 = new AlertDialog.Builder(HomeActivity.this);
LayoutInflater inflater = HomeActivity.this.getLayoutInflater();
ViewGroup parent = null;
builder2.setView(inflater.inflate(R.layout.inputtype, parent, false));
final EditText tagname = (EditText)findViewById(R.id.uname);
builder2.setPositiveButton("OK", new DialogInterface.OnClickListener()
{
@Override
public void onClick(DialogInterface dialog, int id) {
String tag = tagname.getText().toString();
Toast.makeText(getApplicationContext(), "U entered "+tag, Toast.LENGTH_LONG).show();
}
})
.setNegativeButton("CANCEL", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
}
})
.show();
}
}
Logcat：
1-11 05:22:45.427: E/AndroidRuntime(2298): FATAL EXCEPTION: main
11-11 05:22:45.427: E/AndroidRuntime(2298): Process: com.example.myapp, PID: 2298
11-11 05:22:45.427: E/AndroidRuntime(2298): java.lang.NullPointerException
11-11 05:22:45.427: E/AndroidRuntime(2298): at com.example.myapp.HomeActivity$3.onClick(HomeActivity.java:278)
11-11 05:22:45.427: E/AndroidRuntime(2298): at com.android.internal.app.AlertController$ButtonHandler.handleMessage(AlertController.java:166)
11-11 05:22:45.427: E/AndroidRuntime(2298): at android.os.Handler.dispatchMessage(Handler.java:102)
11-11 05:22:45.427: E/AndroidRuntime(2298): at android.os.Looper.loop(Looper.java:136)
11-11 05:22:45.427: E/AndroidRuntime(2298): at android.app.ActivityThread.main(ActivityThread.java:5017)
11-11 05:22:45.427: E/AndroidRuntime(2298): at java.lang.reflect.Method.invokeNative(Native Method)
11-11 05:22:45.427: E/AndroidRuntime(2298): at java.lang.reflect.Method.invoke(Method.java:515)
11-11 05:22:45.427: E/AndroidRuntime(2298): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
11-11 05:22:45.427: E/AndroidRuntime(2298): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
11-11 05:22:45.427: E/AndroidRuntime(2298): at dalvik.system.NativeStart.main(Native Method)
新的logcat
11-11 06:06:35.917: E/AndroidRuntime(4530): FATAL EXCEPTION: main
11-11 06:06:35.917: E/AndroidRuntime(4530): Process: com.example.myapp, PID: 4530
11-11 06:06:35.917: E/AndroidRuntime(4530): java.lang.NullPointerException
11-11 06:06:35.917: E/AndroidRuntime(4530): at com.example.myapp.HomeActivity$3.onClick(HomeActivity.java:282)
11-11 06:06:35.917: E/AndroidRuntime(4530): at com.android.internal.app.AlertController$ButtonHandler.handleMessage(AlertController.java:166)
11-11 06:06:35.917: E/AndroidRuntime(4530): at android.os.Handler.dispatchMessage(Handler.java:102)
11-11 06:06:35.917: E/AndroidRuntime(4530): at android.os.Looper.loop(Looper.java:136)
11-11 06:06:35.917: E/AndroidRuntime(4530): at android.app.ActivityThread.main(ActivityThread.java:5017)
11-11 06:06:35.917: E/AndroidRuntime(4530): at java.lang.reflect.Method.invokeNative(Native Method)
11-11 06:06:35.917: E/AndroidRuntime(4530): at java.lang.reflect.Method.invoke(Method.java:515)
11-11 06:06:35.917: E/AndroidRuntime(4530): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
11-11 06:06:35.917: E/AndroidRuntime(4530): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
11-11 06:06:35.917: E/AndroidRuntime(4530): at dalvik.system.NativeStart.main(Native Method)
布局：
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<ImageView
android:id="@+id/dispimg"
android:layout_width="match_parent"
android:layout_height="64dp"
android:background="#d1d1d1"
android:contentDescription="@string/app_name"
android:scaleType="center"
android:src="@drawable/addme" />
<EditText
android:id="@+id/uname"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginBottom="10dp"
android:layout_marginLeft="10dp"
android:layout_marginRight="10dp"
android:layout_marginTop="16dp"
android:inputType="text"
android:background="@drawable/textfield" />
</LinearLayout>
新代码：
@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if(requestCode == 1 && resultCode == RESULT_OK){
String temp = data.getStringExtra("selectedType");
AlertDialog.Builder builder2 = new AlertDialog.Builder(HomeActivity.this);
LayoutInflater inflater = HomeActivity.this.getLayoutInflater();
ViewGroup parent = null;
View view = inflater.inflate(R.layout.inputtype, parent, true);
final EditText tagname = (EditText)findViewById(R.id.uname);
builder2.setView(view);
builder2.setPositiveButton("OK", new DialogInterface.OnClickListener()
{
@Override
public void onClick(DialogInterface dialog, int id) {
String tag = tagname.getText().toString();
Toast.makeText(getApplicationContext(), "U entered "+tag, Toast.LENGTH_LONG).show();
}
})
.setNegativeButton("CANCEL", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
}
})
.show();
}
}
new logcat：
11-11 06:58:49.804: E/AndroidRuntime(7148): FATAL EXCEPTION: main
11-11 06:58:49.804: E/AndroidRuntime(7148): Process: com.example.myapp, PID: 7148
11-11 06:58:49.804: E/AndroidRuntime(7148): java.lang.NullPointerException
11-11 06:58:49.804: E/AndroidRuntime(7148): at com.example.myapp.HomeActivity$3.onClick(HomeActivity.java:288)
11-11 06:58:49.804: E/AndroidRuntime(7148): at com.android.internal.app.AlertController$ButtonHandler.handleMessage(AlertController.java:166)
11-11 06:58:49.804: E/AndroidRuntime(7148): at android.os.Handler.dispatchMessage(Handler.java:102)
11-11 06:58:49.804: E/AndroidRuntime(7148): at android.os.Looper.loop(Looper.java:136)
11-11 06:58:49.804: E/AndroidRuntime(7148): at android.app.ActivityThread.main(ActivityThread.java:5017)
11-11 06:58:49.804: E/AndroidRuntime(7148): at java.lang.reflect.Method.invokeNative(Native Method)
11-11 06:58:49.804: E/AndroidRuntime(7148): at java.lang.reflect.Method.invoke(Method.java:515)
11-11 06:58:49.804: E/AndroidRuntime(7148): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
11-11 06:58:49.804: E/AndroidRuntime(7148): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
11-11 06:58:49.804: E/AndroidRuntime(7148): at dalvik.system.NativeStart.main(Native Method)
答案 0 :(得分：3)
您的editText属于AlertDialog，因此代码中的跟随行为空：
final EditText tagname = (EditText)findViewById(R.id.uname);
所以你得到NPE
String tag = tagname.getText().toString();
您需要以下代码：
View view = inflater.inflate(R.layout.inputtype, parent, false)
builder2.setView(view);
和
final EditText tagname = (EditText)view.findViewById(R.id.uname);
因此您的代码必须如下：
AlertDialog.Builder builder2 = new AlertDialog.Builder(HomeActivity.this);
LayoutInflater inflater = HomeActivity.this.getLayoutInflater();
ViewGroup parent = null;
View view = inflater.inflate(R.layout.inputtype, parent, false);
final EditText tagname = (EditText)view.findViewById(R.id.uname);
builder2.setView(view);
builder2.setPositiveButton("OK", new DialogInterface.OnClickListener()
{
@Override
public void onClick(DialogInterface dialog, int id) {
String tag = tagname.getText().toString();
Toast.makeText(getApplicationContext(), "U entered "+tag, Toast.LENGTH_LONG).show();
}
})
.setNegativeButton("CANCEL", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
}
})
.show();