Android 游标和SimpleCursorAdapter
可能重复:Android 游标和SimpleCursorAdapter,android,sqlite,simplecursoradapter,Android,Sqlite,Simplecursoradapter,可能重复: 我试图将数据库的值返回到listview,但遇到了一个错误。我使用游标从表中获取数据,使用SimpleCursorAdapter读取游标。这是执行此操作的方法: public void getData(){ String[] columns = new String[] {ModuleDB.KEY_ROWID, ModuleDB.KEY_MODCODE, ModuleDB.KEY_MODNAME,
我试图将数据库的值返回到listview,但遇到了一个错误。我使用游标从表中获取数据,使用SimpleCursorAdapter读取游标。这是执行此操作的方法:
public void getData(){
String[] columns = new String[] {ModuleDB.KEY_ROWID,
ModuleDB.KEY_MODCODE,
ModuleDB.KEY_MODNAME,
ModuleDB.KEY_LECPRAC,
ModuleDB.KEY_DAYS,
ModuleDB.KEY_TIMESTART,
ModuleDB.KEY_TIMEEND,
ModuleDB.KEY_LOCATION,
ModuleDB.KEY_INFO};
int[] to = new int[]{R.id.modcode_entry,
R.id.modname_entry,
R.id.modlecprac_entry,
R.id.modday_entry,
R.id.modtimestart_entry,
R.id.modtimeend_entry,
R.id.modlocation_entry,
R.id.modaddinfo_entry};
Cursor curs = myDatabase.query(ModuleDB.DB_TABLE, columns, null, null, null, null, null);
if (curs != null)
curs.moveToFirst();
SimpleCursorAdapter dataSource = new SimpleCursorAdapter(ModuleDataSource.this, R.layout.list_entry, curs, columns, to);
this.setListAdapter(dataSource);
// Make sure to close the cursor
curs.close();
}
此方法导致异常:“onCreate()之前的活动无法使用系统服务”
有人能帮我吗?我找不到任何关于游标和游标适配器的好教程,我真的完全迷路了
编辑:
这可能会有帮助
MainActivity.java
public class MainActivity extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ModuleDataSource dbinfo = new ModuleDataSource(this);
dbinfo.open();
dbinfo.getData();
dbinfo.close();
}
public class ModuleDataSource extends ListActivity{
private SQLiteDatabase myDatabase;
private ModuleDB myhelper;
public ModuleDataSource(Context context){
myhelper = new ModuleDB(context);
}
public void open() throws SQLException { //Open the database for writing
myDatabase = myhelper.getWritableDatabase();
}
public void close(){ //Close the database
myhelper.close();
}
public void getData(){
String[] columns = new String[] {ModuleDB.KEY_ROWID,
ModuleDB.KEY_MODCODE,
ModuleDB.KEY_MODNAME,
ModuleDB.KEY_LECPRAC,
ModuleDB.KEY_DAYS,
ModuleDB.KEY_TIMESTART,
ModuleDB.KEY_TIMEEND,
ModuleDB.KEY_LOCATION,
ModuleDB.KEY_INFO};
int[] to = new int[]{R.id.modcode_entry,
R.id.modname_entry,
R.id.modlecprac_entry,
R.id.modday_entry,
R.id.modtimestart_entry,
R.id.modtimeend_entry,
R.id.modlocation_entry,
R.id.modaddinfo_entry};
Cursor curs = myDatabase.query(ModuleDB.DB_TABLE, columns, null, null, null, null, null);
startManagingCursor(curs);
if (curs != null)
curs.moveToFirst();
SimpleCursorAdapter dataSource = new SimpleCursorAdapter(ModuleDataSource.this, R.layout.list_entry, curs, columns, to);
setListAdapter(dataSource);
}
}
ModuleDataSource.java
public class MainActivity extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ModuleDataSource dbinfo = new ModuleDataSource(this);
dbinfo.open();
dbinfo.getData();
dbinfo.close();
}
public class ModuleDataSource extends ListActivity{
private SQLiteDatabase myDatabase;
private ModuleDB myhelper;
public ModuleDataSource(Context context){
myhelper = new ModuleDB(context);
}
public void open() throws SQLException { //Open the database for writing
myDatabase = myhelper.getWritableDatabase();
}
public void close(){ //Close the database
myhelper.close();
}
public void getData(){
String[] columns = new String[] {ModuleDB.KEY_ROWID,
ModuleDB.KEY_MODCODE,
ModuleDB.KEY_MODNAME,
ModuleDB.KEY_LECPRAC,
ModuleDB.KEY_DAYS,
ModuleDB.KEY_TIMESTART,
ModuleDB.KEY_TIMEEND,
ModuleDB.KEY_LOCATION,
ModuleDB.KEY_INFO};
int[] to = new int[]{R.id.modcode_entry,
R.id.modname_entry,
R.id.modlecprac_entry,
R.id.modday_entry,
R.id.modtimestart_entry,
R.id.modtimeend_entry,
R.id.modlocation_entry,
R.id.modaddinfo_entry};
Cursor curs = myDatabase.query(ModuleDB.DB_TABLE, columns, null, null, null, null, null);
startManagingCursor(curs);
if (curs != null)
curs.moveToFirst();
SimpleCursorAdapter dataSource = new SimpleCursorAdapter(ModuleDataSource.this, R.layout.list_entry, curs, columns, to);
setListAdapter(dataSource);
}
}
编辑2:Logcat
11-06 23:24:07.885: D/AndroidRuntime(887): Shutting down VM
11-06 23:24:07.885: W/dalvikvm(887): threadid=1: thread exiting with uncaught exception (group=0x4001d800)
11-06 23:24:07.895: E/AndroidRuntime(887): FATAL EXCEPTION: main
11-06 23:24:07.895: E/AndroidRuntime(887): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.adoherty.assignment3/com.adoherty.assignment3.MainActivity}:
java.lang.IllegalStateException: System services not available to Activities before onCreate()
11-06 23:24:07.895: E/AndroidRuntime(887): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
11-06 23:24:07.895: E/AndroidRuntime(887): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
11-06 23:24:07.895: E/AndroidRuntime(887): at android.app.ActivityThread.access$2300(ActivityThread.java:125)
11-06 23:24:07.895: E/AndroidRuntime(887): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
11-06 23:24:07.895: E/AndroidRuntime(887): at android.os.Handler.dispatchMessage(Handler.java:99)
11-06 23:24:07.895: E/AndroidRuntime(887): at android.os.Looper.loop(Looper.java:123)
11-06 23:24:07.895: E/AndroidRuntime(887): at android.app.ActivityThread.main(ActivityThread.java:4627)
11-06 23:24:07.895: E/AndroidRuntime(887): at java.lang.reflect.Method.invokeNative(Native Method)
11-06 23:24:07.895: E/AndroidRuntime(887): at java.lang.reflect.Method.invoke(Method.java:521)
11-06 23:24:07.895: E/AndroidRuntime(887): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
11-06 23:24:07.895: E/AndroidRuntime(887): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
11-06 23:24:07.895: E/AndroidRuntime(887): at dalvik.system.NativeStart.main(Native Method)
11-06 23:24:07.895: E/AndroidRuntime(887): Caused by: java.lang.IllegalStateException: System services not available to Activities before onCreate()
11-06 23:24:07.895: E/AndroidRuntime(887): at android.app.Activity.getSystemService(Activity.java:3526)
11-06 23:24:07.895: E/AndroidRuntime(887): at android.widget.ResourceCursorAdapter.<init>(ResourceCursorAdapter.java:49)
11-06 23:24:07.895: E/AndroidRuntime(887): at android.widget.SimpleCursorAdapter.<init>(SimpleCursorAdapter.java:84)
11-06 23:24:07.895: E/AndroidRuntime(887): at com.adoherty.assignment3.ModuleDataSource.getData(ModuleDataSource.java:74)
11-06 23:24:07.895: E/AndroidRuntime(887): at com.adoherty.assignment3.MainActivity.onCreate(MainActivity.java:17)
11-06 23:24:07.895: E/AndroidRuntime(887): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
11-06 23:24:07.895: E/AndroidRuntime(887): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
11-06 23:24:07.895: E/AndroidRuntime(887): ... 11 more
11-06 23:24:07.885:D/AndroidRuntime(887):关闭虚拟机
11-06 23:24:07.885:W/dalvikvm(887):threadid=1:线程以未捕获异常退出(组=0x4001d800)
11-06 23:24:07.895:E/AndroidRuntime(887):致命异常:主
11-06 23:24:07.895:E/AndroidRuntime(887):java.lang.RuntimeException:无法启动活动组件信息{com.adoherty.assignment3/com.adoherty.assignment3.MainActivity}:
java.lang.IllegalStateException:onCreate()之前的活动无法使用系统服务
11-06 23:24:07.895:E/AndroidRuntime(887):在android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
11-06 23:24:07.895:E/AndroidRuntime(887):在android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
11-06 23:24:07.895:E/AndroidRuntime(887):在android.app.ActivityThread.access$2300(ActivityThread.java:125)
11-06 23:24:07.895:E/AndroidRuntime(887):在android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
11-06 23:24:07.895:E/AndroidRuntime(887):在android.os.Handler.dispatchMessage(Handler.java:99)上
11-06 23:24:07.895:E/AndroidRuntime(887):在android.os.Looper.loop(Looper.java:123)上
11-06 23:24:07.895:E/AndroidRuntime(887):位于android.app.ActivityThread.main(ActivityThread.java:4627)
11-06 23:24:07.895:E/AndroidRuntime(887):位于java.lang.reflect.Method.Invokenactive(本机方法)
11-06 23:24:07.895:E/AndroidRuntime(887):位于java.lang.reflect.Method.invoke(Method.java:521)
11-06 23:24:07.895:E/AndroidRuntime(887):在com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
11-06 23:24:07.895:E/AndroidRuntime(887):在com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
11-06 23:24:07.895:E/AndroidRuntime(887):在dalvik.system.NativeStart.main(本机方法)
11-06 23:24:07.895:E/AndroidRuntime(887):原因:java.lang.IllegalStateException:onCreate()之前的活动无法使用系统服务
11-06 23:24:07.895:E/AndroidRuntime(887):在android.app.Activity.getSystemService(Activity.java:3526)上
11-06 23:24:07.895:E/AndroidRuntime(887):位于android.widget.ResourceCursorAdapter.(ResourceCursorAdapter.java:49)
11-06 23:24:07.895:E/AndroidRuntime(887):在android.widget.SimpleCursorAdapter。(SimpleCursorAdapter.java:84)
11-06 23:24:07.895:E/AndroidRuntime(887):在com.adoherty.assignment3.ModuleDataSource.getData(ModuleDataSource.java:74)
11-06 23:24:07.895:E/AndroidRuntime(887):位于com.adoherty.assignment3.MainActivity.onCreate(MainActivity.java:17)
11-06 23:24:07.895:E/AndroidRuntime(887):在android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
11-06 23:24:07.895:E/AndroidRuntime(887):在android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
11-06 23:24:07.895:E/AndroidRuntime(887):。。。还有11个
您正在活动构造函数中执行某些操作,应该改为在onCreate()中执行
这可能与此问题相同:您正在活动构造函数中执行某些操作,这些操作应该在onCreate()中完成
这可能与此问题相同:
模块化数据源扩展ListActivity
。。您正在活动中创建该活动的实例。。不能将活动实例化为这样的对象
您的ListActivity可能正在尝试进行一些系统调用,它通常会在后台自动为您进行这些调用。由于您正试图将ListActivity实例化为对象,因此正常的活动过程不会发生
您应该将ListActivity中的内容移动到主活动中,并使主活动成为ListActivity
大概是这样的:
public class MainActivity extends ListActivity {
private SQLiteDatabase myDatabase;
private ModuleDB myhelper;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
myhelper = new ModuleDB(this);
open();
getData();
close();
}
public void open() throws SQLException { //Open the database for writing
myDatabase = myhelper.getWritableDatabase();
}
public void close(){ //Close the database
myhelper.close();
}
public void getData(){
String[] columns = new String[] {ModuleDB.KEY_ROWID,
ModuleDB.KEY_MODCODE,
ModuleDB.KEY_MODNAME,
ModuleDB.KEY_LECPRAC,
ModuleDB.KEY_DAYS,
ModuleDB.KEY_TIMESTART,
ModuleDB.KEY_TIMEEND,
ModuleDB.KEY_LOCATION,
ModuleDB.KEY_INFO};
int[] to = new int[]{R.id.modcode_entry,
R.id.modname_entry,
R.id.modlecprac_entry,
R.id.modday_entry,
R.id.modtimestart_entry,
R.id.modtimeend_entry,
R.id.modlocation_entry,
R.id.modaddinfo_entry};
Cursor curs = myDatabase.query(ModuleDB.DB_TABLE, columns, null, null, null, null, null);
startManagingCursor(curs);
SimpleCursorAdapter dataSource = new SimpleCursorAdapter(ModuleDataSource.this, R.layout.list_entry, curs, columns, to);
setListAdapter(dataSource);
}
}
ModuleDataSource扩展了ListActivity
。。您正在活动中创建该活动的实例。。不能将活动实例化为这样的对象
您的ListActivity可能正在尝试进行一些系统调用,它通常会在后台自动为您进行这些调用。由于您正试图将ListActivity实例化为对象,因此正常的活动过程不会发生
您应该将ListActivity中的内容移动到主活动中,并使主活动成为ListActivity
大概是这样的:
public class MainActivity extends ListActivity {
private SQLiteDatabase myDatabase;
private ModuleDB myhelper;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
myhelper = new ModuleDB(this);
open();
getData();
close();
}
public void open() throws SQLException { //Open the database for writing
myDatabase = myhelper.getWritableDatabase();
}
public void close(){ //Close the database
myhelper.close();
}
public void getData(){
String[] columns = new String[] {ModuleDB.KEY_ROWID,
ModuleDB.KEY_MODCODE,
ModuleDB.KEY_MODNAME,
ModuleDB.KEY_LECPRAC,
ModuleDB.KEY_DAYS,
ModuleDB.KEY_TIMESTART,
ModuleDB.KEY_TIMEEND,
ModuleDB.KEY_LOCATION,
ModuleDB.KEY_INFO};
int[] to = new int[]{R.id.modcode_entry,
R.id.modname_entry,
R.id.modlecprac_entry,
R.id.modday_entry,
R.id.modtimestart_entry,
R.id.modtimeend_entry,
R.id.modlocation_entry,
R.id.modaddinfo_entry};
Cursor curs = myDatabase.query(ModuleDB.DB_TABLE, columns, null, null, null, null, null);
startManagingCursor(curs);
SimpleCursorAdapter dataSource = new SimpleCursorAdapter(ModuleDataSource.this, R.layout.list_entry, curs, columns, to);
setListAdapter(dataSource);
}
}
类似于将对
getData()
的调用移动到onCreate()
时发生的问题?您无法执行以下操作。。。ModuleDataSource dbinfo=新ModuleDataSource(此);-您的ModuleDasSource
扩展了ListActivity
,您不能使用new
创建任何类型的活动的实例。此外,您决不能尝试从活动本身内部以外的任何地方调用属于该活动的方法或访问字段。类似于将对getData()
的调用移动到onCreate()
时发生的问题,您无法执行以下操作。。。ModuleDataSource dbinfo=新ModuleDataSource(此);-您的ModuleDasSource
扩展了ListActivity
,您不能使用new
创建任何类型的活动的实例。此外,决不能尝试调用属于