我是 Android 新手,在在这里提问之前我正在谷歌搜索,但在这个问题上我找不到答案。 (这个 stackoverflow.com/questions/4195089 也没有答案)。
In my test app on emulator i have error ERROR/Cursor(1512): Invalid statement in fillWindow() on LogCat when i press back button on second activity.
11-23 19:06:05.050: DEBUG/TestDB/Debug/MainActivity(1512): onCreate
11-23 19:06:06.820: DEBUG/TestDB/Debug/MainActivity(1512): openDataBase
11-23 19:06:07.240: DEBUG/TestDB/Debug/MainActivity(1512): String[] from
11-23 19:06:07.270: DEBUG/TestDB/Debug/MainActivity(1512): SimpleCursorAdapter
11-23 19:06:07.500: DEBUG/TestDB/Debug/MainActivity(1512): myDbHelper.close
11-23 19:06:07.520: DEBUG/TestDB/Debug/MainActivity(1512): onStart
11-23 19:06:07.551: DEBUG/TestDB/Debug/MainActivity(1512): onResume
11-23 19:06:09.040: INFO/ActivityManager(587): Displayed activity ru.olegi/.MainActivity: 7962 ms
11-23 19:06:11.850: INFO/ActivityManager(587): Starting activity: Intent { comp={ru.olegi/ru.olegi.AnotherActivity} }
11-23 19:06:12.100: DEBUG/TestDB/Debug/AnotherActivity(1512): onCreate
11-23 19:06:12.970: INFO/ActivityManager(587): Displayed activity ru.olegi/.AnotherActivity: 1100 ms
11-23 19:06:14.550: ERROR/Cursor(1512): Invalid statement in fillWindow()
11-23 19:06:14.590: DEBUG/TestDB/Debug/MainActivity(1512): onStart
11-23 19:06:14.600: DEBUG/TestDB/Debug/MainActivity(1512): onResume
All code stored in onCreate. So when i press back, ListView is empty. For fix this i move code to onStart. Here is log for this and again have Invalid statement in fillWindow()
11-23 19:26:06.280: DEBUG/TestDB/Debug/MainActivity(6597): onCreate
11-23 19:26:06.462: DEBUG/TestDB/Debug/MainActivity(6597): onStart
11-23 19:26:06.700: DEBUG/TestDB/Debug/MainActivity(6597): openDataBase
11-23 19:26:06.740: DEBUG/TestDB/Debug/MainActivity(6597): String[] from
11-23 19:26:06.750: DEBUG/TestDB/Debug/MainActivity(6597): SimpleCursorAdapter
11-23 19:26:06.981: DEBUG/TestDB/Debug/MainActivity(6597): myDbHelper.close
11-23 19:26:07.010: DEBUG/TestDB/Debug/MainActivity(6597): onResume
11-23 19:26:08.030: INFO/ActivityManager(587): Displayed activity ru.olegi/.MainActivity: 3876 ms
11-23 19:26:15.419: INFO/ActivityManager(587): Starting activity: Intent { comp={ru.olegi/ru.olegi.AnotherActivity} }
11-23 19:26:15.770: DEBUG/TestDB/Debug/AnotherActivity(6597): onCreate
11-23 19:26:16.440: INFO/ActivityManager(587): Displayed activity ru.olegi/.AnotherActivity: 1001 ms
11-23 19:26:17.860: ERROR/Cursor(6597): Invalid statement in fillWindow()
11-23 19:26:17.870: DEBUG/TestDB/Debug/MainActivity(6597): onStart
11-23 19:26:18.260: DEBUG/TestDB/Debug/MainActivity(6597): openDataBase
11-23 19:26:18.290: DEBUG/TestDB/Debug/MainActivity(6597): String[] from
11-23 19:26:18.310: DEBUG/TestDB/Debug/MainActivity(6597): SimpleCursorAdapter
11-23 19:26:18.670: DEBUG/TestDB/Debug/MainActivity(6597): myDbHelper.close
11-23 19:26:18.700: DEBUG/TestDB/Debug/MainActivity(6597): onResume
这段代码
package ru.olegi;
import java.io.IOException;
import android.app.Activity;
import android.content.Intent;
import android.database.Cursor;
import android.database.SQLException;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;
public class MainActivity extends Activity {
/** Called when the activity is first created. */
private DatabaseHelper myDbHelper;
private ListView lv1;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Log.d("TestDB/Debug/MainActivity", "onCreate");
setContentView(R.layout.main);
}
@Override
public void onStart() {
super.onStart();
Log.d("TestDB/Debug/MainActivity", "onStart");
// DATABASE OPEN - START
DatabaseHelper myDbHelper = new DatabaseHelper(this);
myDbHelper = new DatabaseHelper(this);
try {
myDbHelper.createDataBase();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
try {
myDbHelper.openDataBase();
}catch(SQLException sqle){
throw sqle;
}
Log.d("TestDB/Debug/MainActivity", "openDataBase");
// DATABASE OPEN - END
Cursor c = myDbHelper.fetchAllFoodname();
startManagingCursor(c);
lv1 = (ListView) findViewById(R.id.ListView01);
String[] from = new String[] { DatabaseHelper.KEY_NAME };
int[] to = new int[] { android.R.id.text1};
Log.d("TestDB/Debug/MainActivity", "String[] from");
SimpleCursorAdapter notes =
new SimpleCursorAdapter(this, android.R.layout.simple_list_item_1, c, from, to);
Log.d("TestDB/Debug/MainActivity", "SimpleCursorAdapter");
lv1.setAdapter(notes);
lv1.setOnItemClickListener(new OnItemClickListener() {
//@Override
public void onItemClick(AdapterView<?> a, View v, int position, long id) {
Intent intent = new Intent();
//getApplicationContext()
intent.setClass(MainActivity.this, AnotherActivity.class);
//intent.putExtra(AnotherActivity.EXT_ID, id);
startActivity(intent);
//finish();
}
});
// DATABASE CLOSE - START
myDbHelper.close();
Log.d("TestDB/Debug/MainActivity", "myDbHelper.close");
// DATABASE CLOSE - END
}
@Override
public void onResume(){
super.onResume();
Log.d("TestDB/Debug/MainActivity", "onResume");
}
@Override
public void onDestroy(){
super.onDestroy();
Log.d("TestDB/Debug/MainActivity", "onDestroy");
}
}
我在这里读到 groups.google.com/group/android-developers/browse_thread/thread/8bec793c626fb405,以修复 fillwindow() 错误需要
简短回答;你的数据库对象
(db) 的范围错误。更长
回答;通过在方法中声明 db
你对 JVM 说,当
该方法完成你的数据库
连接(db)不再有用。
你应该做的是声明 db at
类级别而不是方法级别
level,在onCreate中创建它,并且
在 onDestroy 中关闭它。
Ok, i move sections // DATABASE OPEN - START and // DATABASE CLOSE - START to onCreate and to onDestory. And now i have exception on start
11-23 19:35:39.310: DEBUG/TestDB/Debug/MainActivity(8975): onCreate
11-23 19:35:40.050: DEBUG/TestDB/Debug/MainActivity(8975): openDataBase
11-23 19:35:40.050: DEBUG/TestDB/Debug/MainActivity(8975): onStart
11-23 19:35:40.090: DEBUG/AndroidRuntime(8975): Shutting down VM
11-23 19:35:40.100: WARN/dalvikvm(8975): threadid=3: thread exiting with uncaught exception (group=0x4000fe70)
11-23 19:35:40.120: ERROR/AndroidRuntime(8975): Uncaught handler: thread main exiting due to uncaught exception
11-23 19:35:40.300: ERROR/AndroidRuntime(8975): java.lang.RuntimeException: Unable to start activity ComponentInfo{ru.olegi/ru.olegi.MainActivity}: java.lang.NullPointerException
11-23 19:35:40.300: ERROR/AndroidRuntime(8975): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2268)
11-23 19:35:40.300: ERROR/AndroidRuntime(8975): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2284)
11-23 19:35:40.300: ERROR/AndroidRuntime(8975): at android.app.ActivityThread.access$1800(ActivityThread.java:112)
11-23 19:35:40.300: ERROR/AndroidRuntime(8975): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1692)
11-23 19:35:40.300: ERROR/AndroidRuntime(8975): at android.os.Handler.dispatchMessage(Handler.java:99)
11-23 19:35:40.300: ERROR/AndroidRuntime(8975): at android.os.Looper.loop(Looper.java:123)
11-23 19:35:40.300: ERROR/AndroidRuntime(8975): at android.app.ActivityThread.main(ActivityThread.java:3948)
11-23 19:35:40.300: ERROR/AndroidRuntime(8975): at java.lang.reflect.Method.invokeNative(Native Method)
11-23 19:35:40.300: ERROR/AndroidRuntime(8975): at java.lang.reflect.Method.invoke(Method.java:521)
11-23 19:35:40.300: ERROR/AndroidRuntime(8975): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:782)
11-23 19:35:40.300: ERROR/AndroidRuntime(8975): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:540)
11-23 19:35:40.300: ERROR/AndroidRuntime(8975): at dalvik.system.NativeStart.main(Native Method)
11-23 19:35:40.300: ERROR/AndroidRuntime(8975): Caused by: java.lang.NullPointerException
11-23 19:35:40.300: ERROR/AndroidRuntime(8975): at ru.olegi.MainActivity.onStart(MainActivity.java:59)
11-23 19:35:40.300: ERROR/AndroidRuntime(8975): at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1205)
11-23 19:35:40.300: ERROR/AndroidRuntime(8975): at android.app.Activity.performStart(Activity.java:3490)
11-23 19:35:40.300: ERROR/AndroidRuntime(8975): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2240)
11-23 19:35:40.300: ERROR/AndroidRuntime(8975): ... 11 more
这是移动数据库部分的代码:
package ru.olegi;
import java.io.IOException;
import android.app.Activity;
import android.content.Intent;
import android.database.Cursor;
import android.database.SQLException;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;
public class MainActivity extends Activity {
/** Called when the activity is first created. */
private DatabaseHelper myDbHelper;
private ListView lv1;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Log.d("TestDB/Debug/MainActivity", "onCreate");
setContentView(R.layout.main);
// DATABASE OPEN - START
DatabaseHelper myDbHelper = new DatabaseHelper(this);
myDbHelper = new DatabaseHelper(this);
try {
myDbHelper.createDataBase();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
try {
myDbHelper.openDataBase();
}catch(SQLException sqle){
throw sqle;
}
Log.d("TestDB/Debug/MainActivity", "openDataBase");
// DATABASE OPEN - END
}
@Override
public void onStart() {
super.onStart();
Log.d("TestDB/Debug/MainActivity", "onStart");
Cursor c = myDbHelper.fetchAllFoodname();
startManagingCursor(c);
lv1 = (ListView) findViewById(R.id.ListView01);
String[] from = new String[] { DatabaseHelper.KEY_NAME };
int[] to = new int[] { android.R.id.text1};
Log.d("TestDB/Debug/MainActivity", "String[] from");
SimpleCursorAdapter notes =
new SimpleCursorAdapter(this, android.R.layout.simple_list_item_1, c, from, to);
Log.d("TestDB/Debug/MainActivity", "SimpleCursorAdapter");
lv1.setAdapter(notes);
lv1.setOnItemClickListener(new OnItemClickListener() {
//@Override
public void onItemClick(AdapterView<?> a, View v, int position, long id) {
Intent intent = new Intent();
//getApplicationContext()
intent.setClass(MainActivity.this, AnotherActivity.class);
//intent.putExtra(AnotherActivity.EXT_ID, id);
startActivity(intent);
//finish();
}
});
}
@Override
public void onResume(){
super.onResume();
Log.d("TestDB/Debug/MainActivity", "onResume");
}
@Override
public void onDestroy(){
super.onDestroy();
Log.d("TestDB/Debug/MainActivity", "onDestroy");
// DATABASE CLOSE - START
myDbHelper.close();
Log.d("TestDB/Debug/MainActivity", "myDbHelper.close");
// DATABASE CLOSE - END
}
}
请帮忙修复fillWindow() 中的语句无效
AnotherActivity - 使用 TextView 很简单,MainActivity 只有 listview + onclick 侦听器