.setAdapter(adapter);给出一个空指针异常

Question

我正在尝试为微调器制作适配器，但是我在answertime.setAdapter（adapter）上得到了一个NullPointerException;这是为什么呢？我的数组在字符串中.xml它们应该在哪里？这是完整的代码。

package lijap.app.starcraft2counters;
import java.io.File;
import android.app.Activity;
import android.os.Bundle;
import android.os.Environment;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemSelectedListener;
import android.widget.ArrayAdapter;
import android.widget.Spinner;
import android.widget.Toast;
public class Settings extends Activity implements OnItemSelectedListener {
Spinner answertime;
Spinner gametime;
Spinner missesallowed;
String[] answerseconds = { "Unlimited", "1 second", "2 seconds",
        "3 seconds", "4 seconds", "5 seconds" };
String[] gameminutes = { "Unlimited", "1 minute", "2 minutes", "3 minutes",
        "4 minutes", "5 minutes" };
String[] numberofmisses = { "Unlimited", "5", "10", "15", "20", "25" };
@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.settings);
    ArrayAdapter adapter = ArrayAdapter.createFromResource(this, R.array.AnswerSeconds, R.layout.custom_spinner_list);
    adapter.setDropDownViewResource(R.layout.custom_spinner);
    answertime.setAdapter(adapter);
    ArrayAdapter adapter2 = ArrayAdapter.createFromResource(this, R.array.GameMinutes, R.layout.custom_spinner_list);
    adapter.setDropDownViewResource(R.layout.custom_spinner);
    gametime.setAdapter(adapter);
    ArrayAdapter adapter3 = ArrayAdapter.createFromResource(this, R.array.NumberOfMisses, R.layout.custom_spinner_list);
    adapter.setDropDownViewResource(R.layout.custom_spinner);
    missesallowed.setAdapter(adapter);

    answertime = (Spinner) findViewById(R.id.s_answertime);
    answertime.setAdapter(adapter);
    answertime.setOnItemSelectedListener(this);

    missesallowed = (Spinner) findViewById(R.id.s_mistakenumber);
    missesallowed.setAdapter(adapter2);
    missesallowed.setOnItemSelectedListener(this);
    gametime = (Spinner) findViewById(R.id.s_gametime);
    gametime.setAdapter(adapter3);
    gametime.setOnItemSelectedListener(this);
}
@Override
public void onItemSelected(AdapterView<?> arg0, View arg1, int arg2,
        long arg3) {
    // TODO Auto-generated method stub
}
@Override
public void onNothingSelected(AdapterView<?> arg0) {
    // TODO Auto-generated method stub
}

}

任何帮助是值得赞赏的 - 利贾普

Answer 1

你需要初始化

Spinner answertime;
Spinner gametime;
Spinner missesallowed;

否则，以下行将为您提供NullPointerException：

answertime.setAdapter(adapter);
gametime.setAdapter(adapter);
missesallowed.setAdapter(adapter);

要初始化 Spinner s，您应该在调用 setContentView 后添加如下内容：

answertime = findViewById(R.id.answertime);
gametime = findViewById(R.id.gametime);
missesallowed = findViewById(R.id.missesallowed);

Answer 2

你从不初始化answertime、gametime或missesallowed。 你需要做这样的事情，

answertime = findViewById(R.id.<the id for this spinner>);
gametime = findViewById(R.id.<the id for this spinner>);
missesallowed = findViewById(R.id.<the id for this spinner>);

在你打电话给他们之前setAdapter()。

另外，这是另一个问题，

ArrayAdapter adapter2 = ArrayAdapter.createFromResource(this, R.array.GameMinutes, R.layout.custom_spinner_list);
adapter.setDropDownViewResource(R.layout.custom_spinner);
gametime.setAdapter(adapter);

请注意，您在引用adapter2中构造了一些东西，然后修改adapter，并将adapter设置为微调器的适配器。 这就是你想要的吗？

Answer 3

还要确保视图可见性设置为 View.VISIBLE