我有一个活动，其中一个viewflipper显示一个包含来自mediastore的艺术家的列表，onitem点击显示所选艺术家的专辑列表，然后显示该专辑中的歌曲。单击一首歌后，它应该使用字符串'title'填充textview。
在此之前，所有游标都工作正常，但最后一个游标似乎以某种方式失去了位置。谁能告诉我为什么logcat告诉我：
05-07 23:58:54.195: E/AndroidRuntime(1961): java.lang.IllegalStateException: Couldn't read row 3, col -1 from CursorWindow. Make sure the Cursor is initialized correctly before accessing data from it.
无法阅读的特定行因所选的艺术家/专辑/歌曲而异。代码如下。非常感谢你的帮助。
package music.flipper;
import android.app.Activity;
import android.database.Cursor;
import android.os.Bundle;
import android.provider.BaseColumns;
import android.provider.MediaStore;
import android.provider.MediaStore.Audio.AlbumColumns;
import android.provider.MediaStore.Audio.ArtistColumns;
import android.provider.MediaStore.Audio.AudioColumns;
import android.provider.MediaStore.MediaColumns;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;
import android.widget.TextView;
import android.widget.ViewFlipper;
public class MusicFlipper extends Activity implements OnItemClickListener {
/** Called when the activity is first created. */
ViewFlipper viewflipper;
Cursor cursor;
private String currentList = "Artist";
@SuppressWarnings("deprecation")
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.flipper);
//set the main view to flipper.
viewflipper = (ViewFlipper) findViewById(R.id.viewFlipper1);
String[] columns = {
BaseColumns._ID,
ArtistColumns.ARTIST
};
//The columns to return for each row.
cursor = managedQuery(MediaStore.Audio.Artists.EXTERNAL_CONTENT_URI,
columns, null, null, null);
ListView listView = (ListView) findViewById(R.id.listView1);
listView.setOnItemClickListener(this);
//set an onitemclicklistener to the first listview in flipper
String[] displayFields = new String[] { ArtistColumns.ARTIST };
//set all the artist names to the array 'displayfields'
int[] displayViews = new int[] { R.id.rowItem };
//number of rows to display and where to bind them
SimpleCursorAdapter adapter = new SimpleCursorAdapter(this,
R.layout.row_item, cursor, displayFields, displayViews);
listView.setAdapter(adapter); }
//Take the display fields array, and bind to the matching display row
@SuppressWarnings("deprecation")
public void onItemClick(AdapterView<?> a, View v, int position, long id) {
if( currentList.equals("Artist")) {
if (cursor.moveToPosition(position)) {
//once an item is clicked, move the cursor to that items position
String where = AudioColumns.ARTIST + "=?";
// Have the cursor look within the artist row?
String whereVal[] = { cursor.getString(cursor
.getColumnIndex(AlbumColumns.ARTIST)) };
//Choose the particular row with the chosen artist's name
String[] columns = {
BaseColumns._ID,
AudioColumns.ALBUM,
};
String orderBy = BaseColumns._ID;
cursor = managedQuery(MediaStore.Audio.Albums.EXTERNAL_CONTENT_URI,
columns, where, whereVal, orderBy);
ListView listView = (ListView) findViewById(R.id.listView2);
listView.setOnItemClickListener(this);
String[] displayFields = new String[] { AudioColumns.ALBUM };
int[] displayViews = new int[] { R.id.rowItem };
SimpleCursorAdapter adapter = new SimpleCursorAdapter(this,
R.layout.row_item, cursor, displayFields, displayViews);
listView.setAdapter(adapter);
currentList = "Album";
viewflipper.showNext();}
} if (currentList.equals("Album")) {
if (cursor.moveToPosition(position)) {
String where = AudioColumns.ALBUM
+ "=?";
String whereVal[] = { cursor.getString(cursor
.getColumnIndex(AlbumColumns.ALBUM)) };
String[] columns = {
MediaColumns.DATA,
BaseColumns._ID,
MediaColumns.TITLE,
MediaColumns.DISPLAY_NAME,
MediaColumns.MIME_TYPE,
};
String orderBy = MediaColumns.TITLE;
cursor = managedQuery(MediaStore.Audio.Media.EXTERNAL_CONTENT_URI,
columns, where, whereVal, orderBy);
ListView listView = (ListView) findViewById(R.id.listView3);
listView.setOnItemClickListener(this);
String[] displayFields = new String[] { MediaColumns.TITLE };
int[] displayViews = new int[] { R.id.rowItem };
SimpleCursorAdapter adapter = new SimpleCursorAdapter(this,
R.layout.row_item, cursor, displayFields, displayViews);
listView.setAdapter(adapter);
currentList.equals("Songs");
viewflipper.showNext();}
} if (currentList.equals("Songs")) {
if (cursor.moveToPosition(position)) {
String title = cursor.getString(cursor.getColumnIndex(MediaColumns.TITLE));
TextView myTextView = (TextView) findViewById(R.id.title);
myTextView.setText(title);
}
}
}
}
答案 0 :(得分：23)
问题不在行中，而在列中。
Couldn't read row 3, **col -1** from CursorWindow. Make sure the Cursor is initialized correctly before accessing data from it.
基本上说光标中不存在MediaColumns.TITLE列。这是真的。它不在您的第一个游标（它正在引用的游标）中。您的其他游标都在if语句中，因此超出范围并仅保留第一个游标。
您可以像在if语句的其他部分中那样重新拉动游标，或者找到某种方法来保留从上一个if语句中获得的游标。
修改
修复非常简单，使光标成为类变量。另外，我不会继续重复使用“光标”。将它们标记为个性和描述性，它将帮助您保持代码的可读性。我可能会这样做：
public class MusicFlipper extends Activity implements OnItemClickListener {
private Cursor artistCursor;
private Cursor albumCursor;
然后你像对待他们一样打电话给他们，但是使用个人名字。
albumCursor = managedQuery(MediaStore.Audio.Media.EXTERNAL_CONTENT_URI,
columns, where, whereVal, orderBy);
由于你将它声明为一个类变量，它将在整个类中可用，所以在最后一部分你会这样做：
if (currentList.equals("Songs")) {
if (albumCursor.moveToPosition(position)) {
String title = albumCursor.getString(albumCursor.getColumnIndex(MediaColumns.TITLE));
TextView myTextView = (TextView) findViewById(R.id.title);
myTextView.setText(title);
}
}