列表视图 + 简单光标适配器不显示数据

Question

好吧，我知道这个问题已经问了很多次这里，我已经尝试了所有的解决方案，但似乎没有工作。我正在跟随学习android的书，我试图用SimpleCursorAdapter的ListView形式显示数据库中的数据来插入它。应该显示数据的屏幕除了标题什么也没显示。

package com.example.yamba;
import android.app.Activity;
import android.database.Cursor;
import android.os.Bundle;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;
public class TimelineActivity extends Activity {
    static final String[] FROM = { StatusData.C_USER,StatusData.C_TEXT, StatusData.C_CREATED_AT};
    static final int[]TO = {R.id.text_user,R.id.text_text,R.id.text_createdAt};
    ListView list;
    Cursor cursor;
    SimpleCursorAdapter adapter;
    @SuppressWarnings("deprecation")
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.timeline);
        list = (ListView) findViewById(R.id.list);

        adapter = new SimpleCursorAdapter(this, R.layout.row, cursor, FROM, TO);
        list.setAdapter(adapter);
        cursor = ((YambaApp) getApplication()).statusData.query();
//      while (cursor.moveToNext()) {
//          String user = cursor.getString(cursor.getColumnIndex(StatusData.C_USER));
//          String text = cursor.getString(cursor.getColumnIndex(StatusData.C_TEXT));
//          list.append(String.format("n%s: %s", user, text));
//      }
    }
}

***Timeline.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:background="@color/my_blue"
    android:orientation="vertical" >
    <TextView
        android:id="@+id/timeline"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:text="@string/Timeline" />
    <ListView
        android:id="@+id/list"
        android:layout_width="match_parent"
        android:layout_height="match_parent" >
    </ListView>
    <!--
<ScrollView 
         android:layout_width="match_parent"
        android:layout_height="match_parent">
    <TextView
        android:id="@+id/timelineView"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />
</ScrollView>
    -->
</LinearLayout>

***row.xml***
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >
    <TextView
        android:id="@+id/text_user"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:text="Slashdot"
        android:textAppearance="?android:attr/textAppearanceLarge" />
    <TextView
        android:id="@+id/text_text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_below="@+id/text_createdAt"
        android:text="A really long example tweet for just test purposes"
        android:textAppearance="?android:attr/textAppearanceMedium" />
    <TextView
        android:id="@+id/text_createdAt"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/text_user"
        android:layout_alignBottom="@+id/text_user"
        android:layout_alignParentRight="true"
        android:text="10 minutes ago"
        android:textAppearance="?android:attr/textAppearanceSmall" />
</RelativeLayout>

我已经粘贴了上面的代码。谁能告诉我是什么把显示器搞乱了?非常感谢您的帮助

谢谢! !

Answer 1

需要在创建SimpleCursorAdapter之前创建游标，否则将向构造函数传递什么。重写如下:

super.onCreate(savedInstanceState);
setContentView(R.layout.timeline);
list = (ListView) findViewById(R.id.list);

cursor = ((YambaApp) getApplication()).statusData.query();
adapter = new SimpleCursorAdapter(this, R.layout.row, cursor, FROM, TO);
list.setAdapter(adapter);