我有Activity使用SimpleCursorAdapter从数据库加载数据。但是每当我测试它时，我都会遇到这样的例外：
07-10 15:53:10.580: D/AndroidRuntime(424): Shutting down VM
07-10 15:53:10.580: W/dalvikvm(424): threadid=1: thread exiting with uncaught exception (group=0x40015560)
07-10 15:53:10.620: E/AndroidRuntime(424): FATAL EXCEPTION: main
07-10 15:53:10.620: E/AndroidRuntime(424): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.emplyeerecords/com.example.emplyeerecords.ShowAllData}: java.lang.IllegalArgumentException: column '_id' does not exist
07-10 15:53:10.620: E/AndroidRuntime(424): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
07-10 15:53:10.620: E/AndroidRuntime(424): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
07-10 15:53:10.620: E/AndroidRuntime(424): at android.app.ActivityThread.access$1500(ActivityThread.java:117)
07-10 15:53:10.620: E/AndroidRuntime(424): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
07-10 15:53:10.620: E/AndroidRuntime(424): at android.os.Handler.dispatchMessage(Handler.java:99)
07-10 15:53:10.620: E/AndroidRuntime(424): at android.os.Looper.loop(Looper.java:123)
07-10 15:53:10.620: E/AndroidRuntime(424): at android.app.ActivityThread.main(ActivityThread.java:3683)
07-10 15:53:10.620: E/AndroidRuntime(424): at java.lang.reflect.Method.invokeNative(Native Method)
07-10 15:53:10.620: E/AndroidRuntime(424): at java.lang.reflect.Method.invoke(Method.java:507)
07-10 15:53:10.620: E/AndroidRuntime(424): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
07-10 15:53:10.620: E/AndroidRuntime(424): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
07-10 15:53:10.620: E/AndroidRuntime(424): at dalvik.system.NativeStart.main(Native Method)
07-10 15:53:10.620: E/AndroidRuntime(424): Caused by: java.lang.IllegalArgumentException: column '_id' does not exist
07-10 15:53:10.620: E/AndroidRuntime(424): at android.database.AbstractCursor.getColumnIndexOrThrow(AbstractCursor.java:314)
07-10 15:53:10.620: E/AndroidRuntime(424): at android.widget.CursorAdapter.init(CursorAdapter.java:111)
07-10 15:53:10.620: E/AndroidRuntime(424): at android.widget.CursorAdapter.<init>(CursorAdapter.java:90)
07-10 15:53:10.620: E/AndroidRuntime(424): at android.widget.ResourceCursorAdapter.<init>(ResourceCursorAdapter.java:47)
07-10 15:53:10.620: E/AndroidRuntime(424): at android.widget.SimpleCursorAdapter.<init>(SimpleCursorAdapter.java:84)
07-10 15:53:10.620: E/AndroidRuntime(424): at com.example.emplyeerecords.ShowAllData.onCreate(ShowAllData.java:31)
07-10 15:53:10.620: E/AndroidRuntime(424): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
07-10 15:53:10.620: E/AndroidRuntime(424): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
07-10 15:53:10.620: E/AndroidRuntime(424): ... 11 more
这是我Activity的代码：
public class ShowAllData extends Activity {
ListView ls;
DatabaseHelper helper = new DatabaseHelper(this);
//adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.show_all);
ls = (ListView) findViewById(R.id.listView1);
//using array adapter
//ArrayAdapter<String> adapter=new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1,helper.getAllName());
//using SimpleCursorAdapter()
Cursor c = helper.CursorGetAllName();
String[] fromCol = new String[]{DatabaseHelper.ID, DatabaseHelper.NAME};
int[] to = new int[]{R.id.textView1, R.id.textView2};
SimpleCursorAdapter adapter = new SimpleCursorAdapter(this, R.layout.show_all_cursor, c, fromCol, to);
ls.setAdapter(adapter);
}
}
我的DatabaseHelper：
public class DatabaseHelper extends SQLiteOpenHelper {
public static final String DBNAME = "EmployeeDetails.db";
//Table declarations
public static final String TABLE_NAME = "tblEmp";
public static final String ID = "empId";
public static final String NAME = "empName";
public static final String PHONE = "empPhone";
public static final String EMAIL = "empEmail";
private static final String CREATE_TABLE = "CREATE TABLE IF NOT EXISTS " + TABLE_NAME + " ( " +
ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
NAME + " VARCHAR(50), " +
PHONE + " INTEGER(12), " +
EMAIL + " VARCHAR(100) )";
SQLiteDatabase db;
ContentValues values = new ContentValues();
Cursor c;
public DatabaseHelper(Context context) {
super(context, DBNAME, null, 1);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(CREATE_TABLE);
}
public Cursor CursorGetAllName() {
Cursor c1 = null;
db = this.getReadableDatabase();
c1 = db.query(TABLE_NAME, new String[]{ID, NAME}, null, null, null, null, null);
if (c1 != null) {
c1.moveToNext();
}
return c1;
}
}
布局R.layout.show_all：
<?xml version="1.0" encoding="utf-8"?><?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">
<ListView
android:id="@+id/listView1"
android:layout_width="match_parent"
android:layout_height="wrap_content"></ListView>
</LinearLayout>
布局R.layout.show_all_cursor：
<?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">
<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<TextView
android:id="@+id/textView2"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</LinearLayout>
我遵循了本教程：tutorialspoint.com
答案 0 :(得分：1)
错误很明显：
java.lang.IllegalArgumentException: column '_id' does not exist
来自doc："The Cursor must include a column named "_id" or this class will not work"
因此，请将empId更改为_id。
再次从文档中"Additionally, using MergeCursor with this class will not work if the merged Cursors have overlapping values in their "_id" columns."
好的是，您还可以使用"as _id"为您自己的ID列创建别名。