小编bha*_*avg的帖子

我是一名经验丰富的java程序员,迈出了Android开发的第一步.我的问题很简单,我的onActivityResult()没有在主活动中执行.这就是我做的.

在MainActivity的onCreate方法中,

Intent intent = new Intent(MainActivity.this, NewScreen.class);

startActivityForResult(intent,RESULT_OK);

我确实覆盖了MainActivity中的onActivityResult方法,

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);

    Log.d("Debug", "Received");
}

在NewScreen活动中,

Intent intent = new Intent(NewScreen.this, MainActivity.class);

this.setResult(RESULT_OK,intent);

Log.d("Debug", "Setting the Result");

finish();

我的清单文件是

<application android:icon="@drawable/icon" android:label="@string/app_name">
    <activity android:name=".MainActivity"
              android:label="@string/app_name">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
    <activity android:name="NewScreen"></activity>

</application>

我已阅读每个论坛并尝试了一切.请帮帮我们.

提前致谢,

我从SQLite表中获取数据时收到空指针异常.我在使用游标获取数据时获得空指针异常,如下面的Cursor c = db.fetchAllData(); 请看下面的精确代码,并向我提出一些想法......

display_transaction.class

public class display_transaction extends Activity {

    DisplayTestDBHelper db;
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.display_listview);

        displayListView();
    }

    public void displayListView() {
        Cursor c= db.fetchAllData();
        String[] columns={db.KEY_ID,db.KEY_DESCRIPTION,db.KEY_AMOUNT};
        int[] id=new int[]{R.id.textView1,R.id.textView2};
        SimpleCursorAdapter s=new SimpleCursorAdapter(this,R.layout.listviewlayout,c,columns,id,0);          

        ListView l=(ListView) findViewById(R.id.listview1);
        l.setAdapter(s);
    }
}

DisplayTestDBHelper.class

public Cursor fetchAllData() {
    String TABLE_NAME="transaction_table";
    SQLiteDatabase db = this.getWritableDatabase();
    Cursor mCursor = db.query(TABLE_NAME, new String[] {KEY_ID, KEY_DESCRIPTION, KEY_AMOUNT}, null, null, null, null, null);

    if (mCursor != null) {
        mCursor.moveToFirst();
    }
    return mCursor;


}

请帮我解决上述问题......提前致谢!!!!