Question

我收到一个错误，经过数周的努力后，我无法弄明白。

我试图做一个片段的例子，当我点击一个按钮时打开另一个对话框片段。

对话框片段有一个edittext视图，我试图用来输入一个名字然后当我点击确定时，片段假设使用一个接口来完成对调用片段的回调，然后从中获取文本edittext并使用它来更新第一个片段布局中textview中的文本，但无论我做什么它都行不通。

我已经没有错误的想法以及如何解决它。任何帮助将不胜感激。

the compiler says line 72 gives the error in DialogFragment (NullPointerException)
(I put a // line 72 comment on that line) 
mListener.setsNewUsername(etEnteredName.getText().toString());// line 72

主要活动

package com.example.fragments;

import android.os.Bundle;
import android.app.Activity;
import android.app.DialogFragment;
import android.widget.TextView;

public class FragmentsActivity extends Activity
implements SignInDialogFragment.MyDialogListener{

String sNewUsername = new String("[Enter Username]");



public void setsNewUsername(String sNewUsername) {
    this.sNewUsername = sNewUsername;
}

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

}

@Override
public void onDialogPositiveClick(DialogFragment dialog) {

    TextView textViewFrag1 =(TextView)dialog.getActivity().findViewById(R.id.textViewFragment1);
    textViewFrag1.setText("Hello" + sNewUsername);
}

@Override
public void onDialogNegativeClick(DialogFragment dialog) {


}

}

主要片段

package com.example.fragments;

import android.app.Activity;
import android.app.Fragment;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;

public class Fragment1 extends Fragment {



public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle     savedInstanceState){

    Log.d("Fragment 1", "onCreateView");
    return inflater.inflate(R.layout.fragment1, container,false);
}

public void onAttach(Activity activity){
    super.onAttach(activity);
    Log.d("Fragment 1", "onAttach");
}

public void onCreate(Bundle savedInstanceState){
    super.onCreate(savedInstanceState);
    Log.d("Fragment 1", "onCreate");

}

public void onActivityCreated(Bundle savedInstanceState){
    super.onActivityCreated(savedInstanceState);
    Log.d("Fragment 1", "onActivityCreated");
}

public void onStart(){
    super.onStart();

    Button btnShowSignin =   (Button)getActivity().findViewById(R.id.btnShowSignInDialog);
    btnShowSignin.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {

            SignInDialogFragment signinDialog = new    SignInDialogFragment();
            signinDialog.show(getFragmentManager(), null);

        }

    });
    Log.d("Fragment 1", "onStart");
}

public void onResume(){
    super.onResume();
    Log.d("Fragment 1", "onResume");


}

@Override
public void onPause() {
    // TODO Auto-generated method stub
    super.onPause();
    Log.d("Fragment 1", "onPause");
}

public void onStop(){
    super.onStop();
    Log.d("Fragment 1", "onStop");

}

public void onDestroyView(){
    super.onDestroyView();
    Log.d("Fragment 1", "onDestroyView");
}

public void onDestroy(){
    super.onDestroy();
    Log.d("Fragment 1", "onDestroy");
}

public void onDetach(){
    super.onDetach();
    Log.d("Fragment 1", "onDetach");
}

}

对话框片段

package com.example.fragments;

import android.app.Activity;
import android.app.AlertDialog;
import android.app.Dialog;
import android.app.DialogFragment;
import android.content.DialogInterface;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.EditText;

public class SignInDialogFragment extends DialogFragment {

View dialogView;
EditText etEnteredName;

String enteredUserName = new String("My Name");

public String getEnteredUserName() {
    return enteredUserName;
}

public void setEnteredUserName(String enteredUserName) {
    this.enteredUserName = enteredUserName;
}

public interface MyDialogListener {
    public void setsNewUsername(String string);
    public void onDialogPositiveClick(DialogFragment dialog);
    public void onDialogNegativeClick(DialogFragment dialog);
}

MyDialogListener mListener;

public void onAttach(Activity activity) {
    super.onAttach(activity);
    // Verify that the host activity implements the callback interface
    try {
        // Instantiate the NoticeDialogListener so we can send events to the host
        mListener = (MyDialogListener) activity;
    } catch (ClassCastException e) {
        // The activity doesn't implement the interface, throw exception
        throw new ClassCastException(activity.toString()
                + " must implement NoticeDialogListener");
    }
}



@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    return super.onCreateView(inflater, container, savedInstanceState);

}

public Dialog onCreateDialog(Bundle savedInstanceState) {

    AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
    LayoutInflater inflater = getActivity().getLayoutInflater();
    builder.setView(inflater.inflate(R.layout.signin, null))

           .setPositiveButton("SignIn", new DialogInterface.OnClickListener() {
               @Override
               public void onClick(DialogInterface dialog, int id) {

                   etEnteredName = (EditText)getActivity().findViewById(R.id.username);

                   mListener.setsNewUsername(etEnteredName.getText().toString());      // line 72

                   mListener.onDialogPositiveClick(SignInDialogFragment.this);

               }
           })
           .setNegativeButton("Cancel", new DialogInterface.OnClickListener() {

               public void onClick(DialogInterface dialog, int id) {

               }

           });      
    return builder.create();
}

@Override
public void dismiss() {
    // TODO Auto-generated method stub
    super.dismiss();
}

@Override
public void onDestroyView() {
    // TODO Auto-generated method stub
    super.onDestroyView();
}

@Override
public void onDetach() {
    // TODO Auto-generated method stub
    super.onDetach();
}

@Override
public void onDismiss(DialogInterface dialog) {
    // TODO Auto-generated method stub
    super.onDismiss(dialog);
}

@Override
public void onStop() {
    // TODO Auto-generated method stub
    super.onStop();
}

@Override
public void onDestroy() {
    // TODO Auto-generated method stub
    super.onDestroy();
}

@Override
public void onPause() {
    // TODO Auto-generated method stub
    super.onPause();

}


}

main.xml中

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="horizontal">

<fragment 
    android:name="com.example.fragments.Fragment1"
    android:id="@+id/fragment1"
    android:layout_weight="1"
    android:layout_width="0dp"
    android:layout_height="match_parent"
    />

</LinearLayout>

fragment1.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="vertical"
android:background="#00FF00">


<TextView 
    android:id="@+id/textViewFragment1"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="SignIn Dialog Text Here"
    android:textColor="#000000"
    android:textSize="25sp"
    />

<Button 
    android:id="@+id/btnShowSignInDialog"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Show SignIn Dialog"
    android:textColor="#000000"
    android:onClick="onClick"
    />

</LinearLayout>

signin.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="wrap_content"
android:layout_height="wrap_content">

<EditText
    android:id="@+id/username"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginTop="16dp"
    android:layout_marginLeft="4dp"
    android:layout_marginRight="4dp"
    android:layout_marginBottom="4dp"
    />

</LinearLayout>

Answer 1

更改此

 etEnteredName = (EditText)getActivity().findViewById(R.id.username);

到

 View v = inflater.inflate(R.layout.signin,null); 
 etEnteredName = (EditText)v.findViewById(R.id.username);

您需要使用膨胀的视图对象来初始化EditText。 EditText位于R.layout.signin。 findViewById查找当前膨胀布局中提到的ID的视图。

将View v;声明为实例变量。

然后

v = inflater.inflate(R.layout.signin,null);
builder.setView(v);

然后

etEnteredName = (EditText)v.findViewById(R.id.username);

使用回调在父片段视图中设置textview文本时获取NullPointerException

1 个答案: