微调项目不起作用

Question

我有一个带有微调器下拉菜单的应用程序。当我从微调器下拉菜单中点击Admin时，它不会转到Admin.class。和教师一样，当我从微调器下拉菜单中点击教师时，它不会转到Student.class。\

我的代码：

public class Home extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_home);

        String[] sp1 = getResources().getStringArray(R.array.Level);
        Spinner spinner = (Spinner)findViewById(R.id.spinner);
        ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,android.R.layout.simple_spinner_item,sp1);
        spinner.setAdapter(adapter);

        spinner.setOnItemSelectedListener(new OnItemSelectedListener() {

            @Override
            public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {

                String s = parent.getItemAtPosition(position).toString();
                if(s=="Admin")
                    startActivity(new Intent(Home.this,Admin.class));
                if(s=="Teacher")
                    startActivity(new Intent(Home.this,Student.class));   
            }

            public void onNothingSelected(AdapterView<?> arg0) {
                // TODO Auto-generated method stub
            }
        });    
    }
}

Answer 1

使用firstString.equals(secondString)函数比较字符串，而不是==运算符。

该函数检查字符串的实际内容，==运算符检查对象的引用是否相等。请注意，字符串常量通常是“实例化”，这样两个具有相同值的常量实际上可以与==进行比较，但最好不要依赖它。

这样做

@Override
public void onItemSelected(AdapterView<?> parent, View view,
                int position, long id) {
    String s = parent.getItemAtPosition(position).toString();
    if(s.equals("Admin"))
        startActivity(new Intent(Home.this,Admin.class));
    if(s.equals("Teacher"))
        startActivity(new Intent(Home.this,Student.class));
}

修改

public class Home extends Activity {
private boolean spinnerAutoSelectionDone = false;
@Override
protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_home);

    String[] sp1 = getResources().getStringArray(R.array.Level);
    Spinner spinner = (Spinner)findViewById(R.id.spinner);
    ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,android.R.layout.simple_spinner_item,sp1);
    spinner.setAdapter(adapter);

    spinner.setOnItemSelectedListener(new OnItemSelectedListener() {

        @Override
        public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {

            if(!spinnerAutoSelectionDone){
                spinnerAutoSelectionDone = true;
                return;
            }

            String s = parent.getItemAtPosition(position).toString();
            if(s.equals("Admin"))
                startActivity(new Intent(Home.this,Admin.class));
            if(s.equals("Teacher"))
                startActivity(new Intent(Home.this,Student.class));   
        }

        public void onNothingSelected(AdapterView<?> arg0) {
            // TODO Auto-generated method stub
        }
    });    
}
}

Answer 2

uses.equals（）方法而不是==运算符.... 因为你在这里比较参考而不是价值。