Question

在我的DataBaseAdapter类中，我编写了一个像这样的方法getAll

public List<AllUserInfor> getAllInfor(int id) {
    List<AllUserInfor> allInfor = new ArrayList<AllUserInfor>();

    String selectQuery = "SELECT Name, Gender FROM MY_TABLE where _id = '"+id+"' ";

    Cursor cursor = sqLiteDatabase.rawQuery(selectQuery, null);


    if (cursor.moveToFirst()) {
        do {
            AllUserInfor alluserinfor = new AllUserInfor();               
            alluserinfor.setName(cursor.getString(1));
            alluserinfor.setGender(cursor.getString(2));                
            allInfor.add(alluserinfor);
        } while (cursor.moveToNext());
    }


    return allInfor;
}

在第二项活动中，我有

@Override
public void onClick(View v) {
    // TODO Auto-generated method stub

    switch (v.getId()) {

    case R.id.btShow:
        // I get id from the first activity
        Bundle extras = getIntent().getExtras();
        id = extras.getInt("Roomid");
        List<AllUserInfor> userInfor = mySQLiteAdapter.getAllInfor(id);
        for (AllUserInfor aui : userInfor){
            tvname.setText(aui.getName());
            tvgender.setText(aui.getGender());

        }
        break;
    }

}

这是我从第一项活动中获取身份的方式

lvroom.setOnItemClickListener(new AdapterView.OnItemClickListener() {

        @Override
        public void onItemClick(AdapterView<?> listView, View view,
                int position, long id) {
            // TODO Auto-generated method stub
            cursor = (Cursor) lvroom.getItemAtPosition(position);
            int item_id = cursor.getInt(cursor.getColumnIndex(SQLiteAdapter.KEY_ID));

            Intent i = new Intent();
            Bundle bundle = new Bundle();
            bundle.putInt("Roomid", item_id);               
            i.putExtras(bundle);
            i.setClass(FirstActivity.this, SecondActivity.class);
            startActivityForResult(i, 0);

        }

在我点击显示按钮inf第二个活动后，没有任何变化，这意味着名称和性别未在第二个布局中显示。我的错误在哪里？帮帮我

这是我的logcat

03-10 18:01:20.790: E/AndroidRuntime(1224): FATAL EXCEPTION: main
03-10 18:01:20.790: E/AndroidRuntime(1224): java.lang.NullPointerException
03-10 18:01:20.790: E/AndroidRuntime(1224):     at com.superman.medreport.SecondActivity.onClick(SecondActivity.java:127)
03-10 18:01:20.790: E/AndroidRuntime(1224):     at android.view.View.performClick(View.java:4204)
03-10 18:01:20.790: E/AndroidRuntime(1224):     at android.view.View$PerformClick.run(View.java:17355)
03-10 18:01:20.790: E/AndroidRuntime(1224):     at android.os.Handler.handleCallback(Handler.java:725)
03-10 18:01:20.790: E/AndroidRuntime(1224):     at android.os.Handler.dispatchMessage(Handler.java:92)
03-10 18:01:20.790: E/AndroidRuntime(1224):     at android.os.Looper.loop(Looper.java:137)
03-10 18:01:20.790: E/AndroidRuntime(1224):     at android.app.ActivityThread.main(ActivityThread.java:5041)
03-10 18:01:20.790: E/AndroidRuntime(1224):     at java.lang.reflect.Method.invokeNative(Native Method)
03-10 18:01:20.790: E/AndroidRuntime(1224):     at java.lang.reflect.Method.invoke(Method.java:511)
03-10 18:01:20.790: E/AndroidRuntime(1224):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
03-10 18:01:20.790: E/AndroidRuntime(1224):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
03-10 18:01:20.790: E/AndroidRuntime(1224):     at dalvik.system.NativeStart.main(Native Method)
03-10 18:01:24.802: E/Trace(1256): error opening trace file: No such file or directory (2)

Answer 1

是因为_id是一个整数吗？你正在传递一个字符串

 '"+id+"'

应该是

  "+id+"

Answer 2

请勿将id值转换为String中Integer的{{1}}。

更改以下条件以获取价值：

"SELECT Name, Gender FROM MY_TABLE where _id = "+id+" ";

只需删除单个" ' "并写为"+id+"而不是'"+id+"'

Answer 3

使用它：

"SELECT Name, Gender FROM MY_TABLE where _id ="+id+";

而不是

"SELECT Name, Gender FROM MY_TABLE where _id = '"+id+"' ";

“选择哪里”不起作用

3 个答案: