Question

我在这段代码的第37行得到了NullPointer异常，就在它所说的

fragment_monday.add(((TextView) editText).getText().toString());

以下是完整档案：

package com.example.classorganizer;

import java.util.List;

import android.app.Dialog;
import android.content.Context;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;

class EditListItemDialog extends Dialog implements View.OnClickListener {

private View editText;

public EditListItemDialog(Context context) {
    super(context);
}

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.edit_text_dialog);//here is your xml with EditText and 'Ok' and 'Cancel' buttons
    View btnOk = findViewById(R.id.button_ok);
    editText = findViewById(R.id.edit_text);
    btnOk.setOnClickListener(this);
}

private List<String> fragment_monday;

public EditListItemDialog(Context context, List<String> fragment_monday) {
    super(context);
    this.fragment_monday = fragment_monday;
}

@Override
public void onClick(View v) {
    fragment_monday.add(((TextView) editText).getText().toString());//here is your updated(or not updated) text
    dismiss();
}
}

当我单击“对话框”中的“确认”按钮更新表格中的行时，出现此错误。该行上的某些对象为null但我不知道如何处理这个... 有人可以帮忙吗？

编辑：如果我发布不同的代码，请告诉我。

这是logcat：

04-20 20:44:11.449: E/AndroidRuntime(2272): FATAL EXCEPTION: main
04-20 20:44:11.449: E/AndroidRuntime(2272): java.lang.NullPointerException
04-20 20:44:11.449: E/AndroidRuntime(2272):     at com.example.classorganizer.EditListItemDialog.onClick(EditListItemDialog.java:37)
04-20 20:44:11.449: E/AndroidRuntime(2272):     at android.view.View.performClick(View.java:2485)
04-20 20:44:11.449: E/AndroidRuntime(2272):     at android.view.View$PerformClick.run(View.java:9080)
04-20 20:44:11.449: E/AndroidRuntime(2272):     at android.os.Handler.handleCallback(Handler.java:587)
04-20 20:44:11.449: E/AndroidRuntime(2272):     at android.os.Handler.dispatchMessage(Handler.java:92)
04-20 20:44:11.449: E/AndroidRuntime(2272):     at android.os.Looper.loop(Looper.java:130)
04-20 20:44:11.449: E/AndroidRuntime(2272):     at android.app.ActivityThread.main(ActivityThread.java:3687)
04-20 20:44:11.449: E/AndroidRuntime(2272):     at java.lang.reflect.Method.invokeNative(Native Method)
04-20 20:44:11.449: E/AndroidRuntime(2272):     at java.lang.reflect.Method.invoke(Method.java:507)
04-20 20:44:11.449: E/AndroidRuntime(2272):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:867)
04-20 20:44:11.449: E/AndroidRuntime(2272):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:625)
04-20 20:44:11.449: E/AndroidRuntime(2272):     at dalvik.system.NativeStart.main(Native Method)

这里我发布xml文件以显示edit_text在那里：

<?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" >
<RelativeLayout
                        android:id="@+id/relativeLayout4"
                        android:layout_width="match_parent"
                        android:layout_height="match_parent"
                        android:layout_weight="1" >
<EditText
    android:id="@+id/edit_text"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:ems="10" >

    <requestFocus />
</EditText>

<Button
    android:id="@+id/button_ok"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="OK" />
</RelativeLayout>
</LinearLayout>

我设置OnItemLongClickListener的文件：

package com.example.classorganizer;


import java.util.ArrayList;

import android.app.ListActivity;
import android.content.Context;
import android.content.Intent;
import android.database.Cursor;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.ListView;
import android.widget.TextView;

import com.cookbook.data.Constants;
import com.cookbook.data.MyDB;




public class Monday extends ListActivity {



private static final int MyMenu = 0;
MyDB dba;
DiaryAdapter myAdapter;

private class MyDiary{
    public MyDiary(String t, String c){
        title=t;
        content=c;

        ListView list = getListView();
        list.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
                public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) {
                    new EditListItemDialog(view.getContext()).show();

                return true;       
            }
        });

}

    public String title;
    public String content;

}

@Override
protected void onCreate(Bundle savedInstanceState) {
    dba = new MyDB(this);
    dba.open();
    setContentView(R.layout.fragment_monday);





    super.onCreate(savedInstanceState);
    myAdapter = new DiaryAdapter(this);
    this.setListAdapter(myAdapter);
}



private class DiaryAdapter extends BaseAdapter {
    private LayoutInflater mInflater;
    private ArrayList<MyDiary> fragment_monday;
    public DiaryAdapter(Context context) {
        mInflater = LayoutInflater.from(context);
        fragment_monday = new ArrayList<MyDiary>();
        getdata();


    }

    public void getdata(){
        Cursor c = dba.getdiaries();
        startManagingCursor(c);
        if(c.moveToFirst()){
            do{
                String title =
                        c.getString(c.getColumnIndex(Constants.TITLE_NAME));
                String content =
                        c.getString(c.getColumnIndex(Constants.CONTENT_NAME));

                MyDiary temp = new MyDiary(title,content);
                fragment_monday.add(temp);
            } while(c.moveToNext());
        }

    }



    @Override
    public int getCount() {return fragment_monday.size();}
    public MyDiary getItem(int i) {return fragment_monday.get(i);}
    public long getItemId(int i) {return i;}
    public View getView(int arg0, View arg1, ViewGroup arg2) {
        final ViewHolder holder;

        View v = arg1;
        if ((v == null) || (v.getTag() == null)) {
            v = mInflater.inflate(R.layout.diaryrow,  null);
            holder = new ViewHolder();
            holder.mTitle = (TextView)v.findViewById(R.id.name);

            v.setTag(holder);
        } else {
            holder = (ViewHolder) v.getTag();
        }

        holder.mdiary = getItem(arg0);
        holder.mTitle.setText(holder.mdiary.title);


        v.setTag(holder);

        return v;


    }

    public class ViewHolder {
        MyDiary mdiary;
        TextView mTitle;


    }

}




/** Called when the user clicks the Edit button */
public void visitDiary(View view) {
    Intent intent = new Intent(this, Diary.class);
    startActivity(intent);
}
/** Called when the user clicks the back button */
public void visitSchedule(View view) {
    Intent intent = new Intent(this, DisplayScheduleScreen.class);
    startActivity(intent);
}


}

这是fragment_monday xml：

的一部分

<RelativeLayout
                        android:id="@+id/relativeLayout4"
                        android:layout_width="0dp"
                        android:layout_height="match_parent"
                        android:layout_weight="1" >

                         <ListView
    android:layout_width="fill_parent"
                    android:gravity="center"
    android:layout_height="fill_parent"
    android:id="@android:id/list"
    android:longClickable="true"
     >

</ListView>



             </RelativeLayout>

Answer 1

我仍然认为fragment_monday为空，在此代码段中：

list.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
            public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) {
                new EditListItemDialog(view.getContext()).show();

            return true;       
        }
    });

您正在使用构造函数EditListItemDialog(Context context)创建对话框但是在onlick中他正在使用fragment_monday。哪个没有初始化。

NullPointerException使用Dialog更新表行

1 个答案: