在我正在开发的Android应用程序中，我正在存储一个条目，然后我想查看它。我能够存储条目（代码不会返回任何错误）但是当我尝试查看条目（即所有条目）时，我会收到一个强制关闭。请帮我。这是我的代码：
package com.ankita.try1;
import android.app.Activity;
import android.database.Cursor;
import android.os.Bundle;
import android.view.ViewGroup.LayoutParams;
import android.widget.LinearLayout;
import android.widget.TextView;
import android.widget.Toast;
public class viewAttendance extends Activity {
LinearLayout l;
quer q;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.view_attendance);
l=(LinearLayout)findViewById(R.id.LinearLayout);
q= new quer(this);
q.open();
Cursor c1;
c1=q.fetchAllTodos();
long co=1;
if(c1!=null)
{
do
{
TextView t;
Cursor c=q.fetchTodo(co);
String name = c.getString(c.getColumnIndexOrThrow(quer.KEY_NAME));
String present = c.getString(c.getColumnIndexOrThrow(quer.KEY_PRESENT));
String total = c.getString(c.getColumnIndexOrThrow(quer.KEY_TOTAL));
int a = (Integer.parseInt(present)/Integer.parseInt(total))*100;
String A = a+"%";
LayoutParams la=new LayoutParams(LayoutParams.WRAP_CONTENT,LayoutParams.WRAP_CONTENT);
t=new TextView(this);
t.setLayoutParams(la);
t.setText(name+" "+A);
l.addView(t);
co++;
}while(co<=c1.getCount());
q.close();
}
else
{
q.close();
Toast.makeText(this, "No Subjects Added", Toast.LENGTH_SHORT).show();
}
}
}
这是我的quer.java（定义了所有函数）：
package com.ankita.try1;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import com.ankita.try1.database1;
public class quer
{
public static final String KEY_ROWID = "_id";
public static final String KEY_NAME = "name";
public static final String KEY_PRESENT = "present";
public static final String KEY_ABSENT = "absent";
public static final String KEY_TOTAL = "total";
/*public static final int KEY_PRESENT=0;
public static final int KEY_ABSENT=0;
public static final int KEY_TOTAL=0;*/
private static final String DATABASE_TABLE = "SUBJECT";
private Context context;
private SQLiteDatabase database;
private database1 dbHelper;
public quer(Context context)
{
this.context = context;
}
public quer open() throws SQLException
{
dbHelper = new database1(context);
database = dbHelper.getWritableDatabase();
return this;
}
public void close()
{
dbHelper.close();
}
private ContentValues createContentValues(String name, String present, String absent,String total)
{
ContentValues values = new ContentValues();
values.put(KEY_NAME, name);
values.put(KEY_PRESENT, present);
values.put(KEY_ABSENT, absent);
values.put(KEY_TOTAL, total);
return values;
}
//TO CREATE A ROW
public long createTodo(String name, String present, String absent,String total) {
ContentValues initialValues = createContentValues(name, present,absent,total);
return database.insert(DATABASE_TABLE, null, initialValues);
}
//TOI DELETE A ROW
public boolean deleteTodo(long rowId)
{
return database.delete(DATABASE_TABLE, KEY_ROWID + "=" + rowId, null) > 0;
}
//FETCH ALL ROWS
public Cursor fetchAllTodos()
{
return database.query(DATABASE_TABLE, new String[] { KEY_ROWID,KEY_NAME, KEY_PRESENT, KEY_ABSENT, KEY_TOTAL}, null, null, null,null, null);
}
//UPDATE THE DATABASE
public boolean updateTodo(long rowId, String name, String present, String absent,String total)
{
ContentValues updateValues = createContentValues(name, present,absent,total);
return database.update(DATABASE_TABLE, updateValues, KEY_ROWID + "="
+ rowId, null) > 0;
}
//FETCH ACC. TO _ID
public Cursor fetchTodo(long rowId) throws SQLException {
Cursor mCursor = database.query(true, DATABASE_TABLE, new String[] {
KEY_ROWID, KEY_NAME, KEY_PRESENT, KEY_ABSENT, KEY_TOTAL },
KEY_ROWID + "=" + rowId, null, null, null, null, null);
if (mCursor != null) {
mCursor.moveToFirst();
}
return mCursor;
}
//FETCH ACC. TO NAME
public Cursor fetchTodo(String name) throws SQLException {
Cursor mCursor = database.query(true, DATABASE_TABLE, new String[] {
KEY_ROWID, KEY_NAME, KEY_PRESENT, KEY_ABSENT, KEY_TOTAL },
KEY_NAME + "=" + name, null, null, null, null, null);
if (mCursor != null) {
mCursor.moveToFirst();
}
return mCursor;
}
}
我无法查看数据库条目，即我没有看到正在执行的viewAttendance活动的任何内容 - 我强行关闭 - 我哪里出错？
这是logcat：
07-05 19:06:16.304: D/AndroidRuntime(29530): Shutting down VM
07-05 19:06:16.304: W/dalvikvm(29530): threadid=1: thread exiting with uncaught exception (group=0x40018578)
07-05 19:06:16.328: E/AndroidRuntime(29530): FATAL EXCEPTION: main
07-05 19:06:16.328: E/AndroidRuntime(29530): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.ankita.try1/com.ankita.try1.viewAttendance}: android.database.CursorIndexOutOfBoundsException: Index 0 requested, with a size of 0
07-05 19:06:16.328: E/AndroidRuntime(29530): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1651)
07-05 19:06:16.328: E/AndroidRuntime(29530): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1667)
07-05 19:06:16.328: E/AndroidRuntime(29530): at android.app.ActivityThread.access$1500(ActivityThread.java:117)
07-05 19:06:16.328: E/AndroidRuntime(29530): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:935)
07-05 19:06:16.328: E/AndroidRuntime(29530): at android.os.Handler.dispatchMessage(Handler.java:99)
07-05 19:06:16.328: E/AndroidRuntime(29530): at android.os.Looper.loop(Looper.java:130)
07-05 19:06:16.328: E/AndroidRuntime(29530): at android.app.ActivityThread.main(ActivityThread.java:3687)
07-05 19:06:16.328: E/AndroidRuntime(29530): at java.lang.reflect.Method.invokeNative(Native Method)
07-05 19:06:16.328: E/AndroidRuntime(29530): at java.lang.reflect.Method.invoke(Method.java:507)
07-05 19:06:16.328: E/AndroidRuntime(29530): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:867)
07-05 19:06:16.328: E/AndroidRuntime(29530): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:625)
07-05 19:06:16.328: E/AndroidRuntime(29530): at dalvik.system.NativeStart.main(Native Method)
07-05 19:06:16.328: E/AndroidRuntime(29530): Caused by: android.database.CursorIndexOutOfBoundsException: Index 0 requested, with a size of 0
07-05 19:06:16.328: E/AndroidRuntime(29530): at android.database.AbstractCursor.checkPosition(AbstractCursor.java:580)
07-05 19:06:16.328: E/AndroidRuntime(29530): at android.database.AbstractWindowedCursor.checkPosition(AbstractWindowedCursor.java:214)
07-05 19:06:16.328: E/AndroidRuntime(29530): at android.database.AbstractWindowedCursor.getString(AbstractWindowedCursor.java:41)
07-05 19:06:16.328: E/AndroidRuntime(29530): at com.ankita.try1.viewAttendance.onCreate(viewAttendance.java:36)
07-05 19:06:16.328: E/AndroidRuntime(29530): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
07-05 19:06:16.328: E/AndroidRuntime(29530): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1615)
07-05 19:06:16.328: E/AndroidRuntime(29530): ... 11 more
答案 0 :(得分：2)
我想回答这个问题，因为它的评论太长了。
首先在线程中访问数据库，您可以使用AsyncTask，Threads或CursorLoaders。
也可以通过光标移动尝试使用cursor.moveToNext()而不是使用do-while使用简单的while并检查它是否不是afterlast：
while(!cursor.isAfterLast){
cursor.moveToNext();
//do-something
}
你也有这个：
c1=q.fetchAllTodos();
long co=1;
if(c1!=null)
{ //something }
您正在检查光标是否为空，但请记住您的光标可能为空，这可能会导致您出现问题（我猜它是您的光标） 所以要修复它，添加如下的验证：
if(c1!=null && c1.getCount()!=0)
{ //something }
还要在非UI线程中更新你不能这样做的View，这样你就需要一个处理程序，一个帖子或其他方法。如果您使用AsyncTask，我建议您在onPostExecute。