java - Android Studio 错误 "Private field ' '“已分配但从未访问过

Question

我正在制作蓝牙应用程序，并且在 Android Studio 中遇到错误。 当我将鼠标悬停在“私有(private)按钮打开、关闭、可见、列表”上时，它告诉我“私有(private)字段”已分配但从未访问过”。 这是什么意思？奇怪的是，该应用程序无法在模拟器中运行，但在我的设备上运行良好。知道我做错了什么吗？

O.T.:如何将代码置于“剧透”模式或类似模式？我不想让论坛充斥着代码:)

主要的Java代码是:

   import android.os.Bundle;
   import android.app.Activity;
   import android.bluetooth.BluetoothAdapter;
   import android.bluetooth.BluetoothDevice;
   import android.content.Intent;
   import android.view.Menu;
   import android.view.View;
   import android.widget.ArrayAdapter;
   import android.widget.Button;
   import android.widget.ListAdapter;
   import android.widget.ListView;
   import android.widget.Toast;

    public class MainActivity extends Activity {

private Button On,Off,Visible,list;
private BluetoothAdapter BA;
private Set<BluetoothDevice>pairedDevices;
private ListView lv;
@Override

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    On = (Button)findViewById(R.id.button1);
    Off = (Button)findViewById(R.id.button2);
    Visible = (Button)findViewById(R.id.button3);
    list = (Button)findViewById(R.id.button4);

    lv = (ListView)findViewById(R.id.listView1);

    BA = BluetoothAdapter.getDefaultAdapter();
}

public void on(View view){
    if (!BA.isEnabled()) {
        Intent turnOn = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
        startActivityForResult(turnOn, 0);
        Toast.makeText(getApplicationContext(),"Turned on"
                ,Toast.LENGTH_LONG).show();
    }
    else{
        Toast.makeText(getApplicationContext(),"Already on",
                Toast.LENGTH_LONG).show();
    }
}
public void list(View view){
    pairedDevices = BA.getBondedDevices();

    ArrayList list = new ArrayList();
    for(BluetoothDevice bt : pairedDevices)
        list.add(bt.getName());

    Toast.makeText(getApplicationContext(),"Showing Paired Devices",
            Toast.LENGTH_SHORT).show();
    final ArrayAdapter adapter = new ArrayAdapter
            (this,android.R.layout.simple_list_item_1, list);
    lv.setAdapter(adapter);

}
public void off(View view){
    BA.disable();
    Toast.makeText(getApplicationContext(),"Turned off" ,
            Toast.LENGTH_LONG).show();
}
public void visible(View view){
    Intent getVisible = new Intent(BluetoothAdapter.
            ACTION_REQUEST_DISCOVERABLE);
    startActivityForResult(getVisible, 0);

}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_main, menu);
    return true;
}

}

Answer 1

您有四个变量:

 private Button On, Off, Visible, list;

您分配所有这些:

 On = (Button)findViewById(R.id.button1);
    Off = (Button)findViewById(R.id.button2);
    Visible = (Button)findViewById(R.id.button3);
    list = (Button)findViewById(R.id.button4);

但你只使用“列表”:

for(BluetoothDevice bt : pairedDevices)
        list.add(bt.getName());

错误(或警告)告诉您不使用变量会浪费它们。现在拆分您的私有(private)变量并且不要分配它们，它应该看起来像这样:

private Button list;
//private Button On, Off, Visible;

然后:

//On = (Button)findViewById(R.id.button1);
//Off = (Button)findViewById(R.id.button2);
//Visible = (Button)findViewById(R.id.button3);
list = (Button)findViewById(R.id.button4);

当您想使用这些变量时，请取消注释它们，然后就可以开始了!