数据库错误:尝试在空对象引用上调用虚拟方法'Cursor .getScene()' [英] Database error: Attempt to invoke virtual method 'Cursor .getScene()' on a null object reference

问题描述

java.lang.NullPointerException:尝试调用虚拟方法'android.database.Cursorcom.example.munna.homeauto.DatabaseCreation.getScene()'在null上对象引用

java.lang.NullPointerException: Attempt to invoke virtual method 'android.database.Cursor com.example.munna.homeauto.DatabaseCreation.getScene()' on a null object reference

public class Server extends Activity {

    DatabaseCreation myDb;
    int i;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //setContentView(R.layout.scenario);

        myDb = new DatabaseCreation(this);

    }

    public void server_check() {
        System.out.println("client");
        int j;
        int k;
        Cursor scene = myDb.getScene();//unfortunetly stops when cursor comes to this step
        while (scene.moveToNext()) {
            System.out.println("client 1");
            for (i = 0; i <= 5; i++) {
                scene.getString(i);
                System.out.println("client 2");
                // my code for server message 
            }

        }

    }
}

推荐答案

if (sence.hasNext()) {
while (scene.moveToNext()) {
    System.out.println("client 1");
    for (i = 0; i <= 5; i++) {
        System.out.println(scene.getString(i));
       }
    }
}

祝你好运:)

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