Android onItemSelected函數無法識別實例變量

Question

我的微調控件的onItemSelected函數無法識別活動中的變量（聲明爲final）。我有onClickListener函數在同一個活動的按鈕識別這些相同的變量。

下面是一些代碼：

public class Currency extends Activity implements OnItemSelectedListener{ 
@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    requestWindowFeature(Window.FEATURE_NO_TITLE); 
    setContentView(R.layout.activity_currency); 
    final TextView tv2 = (TextView) findViewById(R.id.textView2); 
    final TextView tv3 = (TextView) findViewById(R.id.textView3); 

} 

@Override 
public void onItemSelected(AdapterView<?> arg0, View v, int position, 
     long arg3) { 
    switch (position) { 
    case 0: 
     tv2.setText("something"); 
     tv3.setText("something"); 
     break; 
    case 1: 
     tv2.setText("something"); 
     tv3.setText("something"); 
    case 2: 
     tv2.setText("something"); 
     tv3.setText("something"); 
     break; 

     default: 
     break; 
    } 

} 

的（靠近每一行）錯誤：「TV2無法解析」在類級

Answer 1

聲明TV2等下方。從的onCreate

刪除聲明

private TextView tv2 

您的代碼必須看起來像下面的代碼

public class Currency extends Activity implements OnItemSelectedListener{ 
private TextView tv2; 
private TextView tv3; 

@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    requestWindowFeature(Window.FEATURE_NO_TITLE); 
    setContentView(R.layout.activity_currency); 
    tv2 = (TextView) findViewById(R.id.textView2); 
    tv3 = (TextView) findViewById(R.id.textView3); 

} 


@Override 
public void onItemSelected(AdapterView<?> arg0, View v, int position, 
     long arg3) { 
    switch (position) { 
    case 0: 
     tv2.setText("something"); 
     tv3.setText("something"); 
     break; 
    case 1: 
     tv2.setText("something"); 
     tv3.setText("something"); 
    case 2: 
     tv2.setText("something"); 
     tv3.setText("something"); 
     break; 

     default: 
     break; 
    } 

}