CursorAdapter的bindView()方法中的NullPointerException [英] NullPointerException in CursorAdapter's bindView() method

问题描述

我的应用程序出现以下错误，我认为这与我制作布局文件或在代码中使用它们的方式有关.

I'm getting the following errors in my app, and I think it has to do with the way I did the layout files, or used them in my code.

05-31 13:39:59.283: E/AndroidRuntime(332): Uncaught handler: thread main exiting due to uncaught exception
05-31 13:39:59.293: E/AndroidRuntime(332): java.lang.NullPointerException
05-31 13:39:59.293: E/AndroidRuntime(332):  at com.dd.qsg.ShowAchievements$AchievementAdapter.bindView(ShowAchievements.java:38)
05-31 13:39:59.293: E/AndroidRuntime(332):  at android.widget.CursorAdapter.getView(CursorAdapter.java:186)
05-31 13:39:59.293: E/AndroidRuntime(332):  at android.widget.AbsListView.obtainView(AbsListView.java:1274)
05-31 13:39:59.293: E/AndroidRuntime(332):  at android.widget.ListView.measureHeightOfChildren(ListView.java:1147)
05-31 13:39:59.293: E/AndroidRuntime(332):  at android.widget.ListView.onMeasure(ListView.java:1060)
05-31 13:39:59.293: E/AndroidRuntime(332):  at android.view.View.measure(View.java:7964)
05-31 13:39:59.293: E/AndroidRuntime(332):  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3023)
05-31 13:39:59.293: E/AndroidRuntime(332):  at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:888)
05-31 13:39:59.293: E/AndroidRuntime(332):  at android.widget.LinearLayout.measureHorizontal(LinearLayout.java:619)
05-31 13:39:59.293: E/AndroidRuntime(332):  at android.widget.LinearLayout.onMeasure(LinearLayout.java:280)
05-31 13:39:59.293: E/AndroidRuntime(332):  at android.view.View.measure(View.java:7964)
05-31 13:39:59.293: E/AndroidRuntime(332):  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3023)
05-31 13:39:59.293: E/AndroidRuntime(332):  at android.widget.FrameLayout.onMeasure(FrameLayout.java:245)
05-31 13:39:59.293: E/AndroidRuntime(332):  at android.view.View.measure(View.java:7964)
05-31 13:39:59.293: E/AndroidRuntime(332):  at android.widget.LinearLayout.measureVertical(LinearLayout.java:464)
05-31 13:39:59.293: E/AndroidRuntime(332):  at android.widget.LinearLayout.onMeasure(LinearLayout.java:278)
05-31 13:39:59.293: E/AndroidRuntime(332):  at android.view.View.measure(View.java:7964)
05-31 13:39:59.293: E/AndroidRuntime(332):  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3023)
05-31 13:39:59.293: E/AndroidRuntime(332):  at android.widget.FrameLayout.onMeasure(FrameLayout.java:245)
05-31 13:39:59.293: E/AndroidRuntime(332):  at android.view.View.measure(View.java:7964)
05-31 13:39:59.293: E/AndroidRuntime(332):  at android.view.ViewRoot.performTraversals(ViewRoot.java:763)
05-31 13:39:59.293: E/AndroidRuntime(332):  at android.view.ViewRoot.handleMessage(ViewRoot.java:1633)
05-31 13:39:59.293: E/AndroidRuntime(332):  at android.os.Handler.dispatchMessage(Handler.java:99)
05-31 13:39:59.293: E/AndroidRuntime(332):  at android.os.Looper.loop(Looper.java:123)
05-31 13:39:59.293: E/AndroidRuntime(332):  at android.app.ActivityThread.main(ActivityThread.java:4363)
05-31 13:39:59.293: E/AndroidRuntime(332):  at java.lang.reflect.Method.invokeNative(Native Method)
05-31 13:39:59.293: E/AndroidRuntime(332):  at java.lang.reflect.Method.invoke(Method.java:521)
05-31 13:39:59.293: E/AndroidRuntime(332):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860)
05-31 13:39:59.293: E/AndroidRuntime(332):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
05-31 13:39:59.293: E/AndroidRuntime(332):  at dalvik.system.NativeStart.main(Native Method)

这是ShowAchievements类:

package com.dd.qsg;

import android.app.ListActivity;
import android.content.Context;
import android.database.Cursor;
import android.graphics.Color;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.CursorAdapter;
import android.widget.TextView;

public class ShowAchievements extends ListActivity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.achievements);

        DatabaseHandler db = new DatabaseHandler(this);
        Cursor cursor = db.getAchievements(this);
        AchievementAdapter cursorAdapter = new AchievementAdapter(this, cursor);

        this.setListAdapter(cursorAdapter);
    } 

    private class AchievementAdapter extends CursorAdapter {
        public AchievementAdapter(Context context, Cursor c) {
            super(context, c);
        }

        @Override
        public void bindView(View v, Context context, Cursor cursor) {
            if(cursor.getString(cursor.getColumnIndex("completed")).equals("yes")) {
                TextView tv = (TextView) v.findViewById(R.id.achView1);
                tv.setTextColor(Color.GREEN);
            }
        }

        @Override
        public View newView(Context context, Cursor cursor, ViewGroup parent) {
            LayoutInflater inflater = LayoutInflater.from(context);
            View v = inflater.inflate(R.layout.achievements, parent, false);
            return v;
        }
    }    
}

这是我的DatabaseHandler类中的getAchievements()方法:

public Cursor getAchievements(Context context) {
    String selectQuery = "SELECT * FROM achievements ORDER BY _id asc";
    SQLiteDatabase db = this.getWritableDatabase();
    return db.rawQuery(selectQuery, null);
}

这是我的achievements布局:

<?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" >

    <ListView
        android:id="@android:id/list"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" />

    <TextView
        android:id="@+id/android:empty"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:text=""/>

</LinearLayout>

这是我的achievements_item布局:

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

    <TextView
        android:id="@+id/achView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="" />

</LinearLayout>

我假设这些错误是由我处理xml文件的方式引起的.我是否应该将achView1 TextView放置在achievements布局内，而不是achievements_item布局内?我应该从achievements中删除空的TextView吗?

I'm assuming these errors are caused by how I did my xml files. Was I supposed to put the achView1 TextView inside of the achievements layout rather than the achievements_item layout? Should I remove the empty TextView from achievements?

推荐答案

v为null和tv is also null ...因此为null指针异常...由于布局文件行的xml错误，我的意思是item.you在newView方法中，应在充气物品时使用R.layout.achievements_item.xml ...

v is null and tv is also null...so null pointer exeption...due to wrong xml refrence of layout file row i mean item.you should use R.layout.achievements_item.xml while inflating item, in newView method...

 View v = inflater.inflate(R.layout.achievements_item, parent, false);
                                    ^^^^^^^^^^^^^^^^^ 

        @Override
        public View newView(Context context, Cursor cursor, ViewGroup parent) {
            LayoutInflater inflater = LayoutInflater.from(context);
            View v = inflater.inflate(R.layout.achievements_item, parent, false);
            return v;
        }

这篇关于CursorAdapter的bindView()方法中的NullPointerException的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！