Question

我已经阅读了很多主题，但是我仍然找不到如何从ListView中的数据库中获取光标的答案。当我将Log.d日志输出到控制台时，但我无法理解如何在ListView中引入“string_word”。我试着用onItemClick做它，但我不知道我需要在方法中写什么:(这是代码：

public class MainActivity extends Activity implements OnClickListener {

final String LOG_TAG = "myLogs";

IdDB idh;
SynDB sqh;
SQLiteDatabase sqdb, iddb;
Button btnOk;
EditText etWord;
String eWord;


public String string_word;
public String[] syns;



public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    etWord = (EditText) findViewById(R.id.etWord);
    btnOk = (Button) this.findViewById(R.id.btnOk);
    ListView lvMain = (ListView) findViewById(R.id.lvMain);
    btnOk.setOnClickListener(btnOkListener);

    //initialize our class-cover IdDB
    idh = new IdDB(this);

    // initialize our class-cover SynDB
    sqh = new SynDB(this);

    // we need db to read and write
    sqdb = sqh.getWritableDatabase();
    iddb = idh.getWritableDatabase();

    // создаем адаптер
    ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
            android.R.layout.simple_list_item_1, syns);

    // присваиваем адаптер списку
    lvMain.setAdapter(adapter);


    setContentView(lvMain);
    lvMain.setOnItemClickListener(new OnItemClickListener()
    {
        @Override
        public void onItemClick(AdapterView<?> arg0, View arg1,int position, long arg3)
        {

        }
    });

}



   public OnClickListener btnOkListener = new OnClickListener(){

        @Override
        public void onClick(View v) {

            eWord = etWord.getText().toString();



            switch (v.getId()){

                case R.id.btnOk:

                    String query = // Long SQL query out "word"-> string_word

                    Log.d(LOG_TAG, query);
                    Log.d(LOG_TAG, "--- Rows in mytable: ---");

                    // делаем запрос всех данных из таблицы words, получаем Cursor
                    Cursor cursor = sqdb.rawQuery(query, null);



                    int wordColIndex = cursor.getColumnIndex(SynDB.Word);
                    while (cursor.moveToNext()) {

                        string_word = cursor.getString(wordColIndex);
                        Log.d(LOG_TAG, "word = "+ string_word);
                        syns = new String[] {string_word};

                    }

                    cursor.close();
                    break;

                default:
                    break;
            } // close switch
        } // close onClick
    };




protected void onStop() {
    // TODO Auto-generated method stub
    super.onStop();
    // закрываем соединения с базой данных
    sqdb.close();
    sqh.close();
}
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}


@Override
public void onClick(View view) {

 }


}

logcat的：

5-10 10:51:19.678    1642-1642/ru.psdevteam.syndicttest.app W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0xb57db4f0)
05-10 10:51:19.678    1642-1642/ru.psdevteam.syndicttest.app E/AndroidRuntime﹕ FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to start activity ComponentInfo{ru.psdevteam.syndicttest.app/ru.psdevteam.syndicttest.app.MainActivity}: java.lang.NullPointerException
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
        at android.app.ActivityThread.access$1500(ActivityThread.java:117)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:130)
        at android.app.ActivityThread.main(ActivityThread.java:3683)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:507)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
        at dalvik.system.NativeStart.main(Native Method)
  Caused by: java.lang.NullPointerException
        at java.util.Arrays$ArrayList.<init>(Arrays.java:47)
        at java.util.Arrays.asList(Arrays.java:169)
        at android.widget.ArrayAdapter.<init>(ArrayAdapter.java:125)
        at ru.psdevteam.syndicttest.app.MainActivity.onCreate(MainActivity.java:57)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)

Answer 1

public String[] syns;

你的syns未初始化。您应该在创建ArrayAdapter之前初始化它

Answer 2

Try to add this pieace of code :
// создаем адаптер
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
 android.R.layout.simple_list_item_1, syns);

// присваиваем адаптер списку
lvMain.setAdapter(adapter);

After this code:
while (cursor.moveToNext()) {
  string_word = cursor.getString(wordColIndex);
  Log.d(LOG_TAG, "word = "+ string_word);
  syns = new String[] {string_word};
}
cursor.close();

Answer 3

您可以将活动的内容视图设置两次：

setContentView(R.layout.main);
setContentView(lvMain);

在我在这里提到的第二行中，您将列表视图设置为活动视图，这是不正确的。每个活动的ContentView应该引用布局，而不仅仅是列表视图。只需从代码中删除第二行并重建它。

您可以在refrence上检查setContentView的定义：

在ListView中输出SQLite并双重覆盖onClick

3 个答案: