Question

我想将listview与ArrayAdapter

一起使用

扫描WiFi后，广播接收器的代码如下

public void onReceive(Context context, Intent intent) {
        // TODO Auto-generated method stub
        scanResultDevices.notifyDataSetInvalidated();
        wifiResults = wm.getScanResults();
        scanResultDevices = new ArrayAdapter<String>(getApplicationContext(), android.R.layout.simple_list_item_1);
        scanResultAdapter = new ArrayAdapter<ScanResult>(getApplicationContext(),android.R.layout.simple_list_item_1);
        Log.e("inside","BD REceiver");
        if(wifiResults != null){
            for(ScanResult s : wifiResults){
                scanResultAdapter.add(s);
                scanResultDevices.add(s.SSID);
            }
        scanResult.setAdapter(scanResultDevices);
        scanResultDevices.notifyDataSetChanged();
        }
        unregisterReceiver(scanComp);
    }

但这显示scanResult.setAdapter(scanResultDevices)

处的空指针异常

我知道如何使用new ArrayAdapter<T>(context, textViewResourceId, objects)。但在这种特殊情况下，我想尝试new ArrayAdapter<T>(context, textViewResourceId)。如果我正在尝试的是不可能的，那么我该怎么做呢？

编辑：

更新了代码

 protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_test);
    View v = findViewById(R.id.dialogtitle);
    scanResult = (ListView) findViewById(R.id.scanResult);

    //scanResult.setAdapter(scanResultDevices);

    AlertDialog.Builder builder = new AlertDialog.Builder(this);
    builder.setMessage("Scan For Device").setCustomTitle(v).setPositiveButton("SCan",this).create();
    builder.show();
}

onClick的代码：

@Override
public void onClick(DialogInterface dialog, int which) {
    // TODO Auto-generated method stub
    wm = (WifiManager) getSystemService(WIFI_SERVICE);
    if(!wm.isWifiEnabled()){
        wm.setWifiEnabled(true);
        Toast.makeText(getApplicationContext(), "Turning on Wifi", Toast.LENGTH_SHORT);
        Log.e("Wifi","Not-on!Enabling");
    }
    MyDialogFragment alert = new MyDialogFragment();
    alert.show(getFragmentManager(), "SCAN_DIALOG");
    wm.startScan();

    registerReceiver(scanComp, new IntentFilter(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION));


//  if(wifiResults.isEmpty())

}

Answer 1

可以简单地说：

ArrayAdapter<YOUR_CLASS> name =   new ArrayAdapter<YOUR_CLASS>(context, textViewResourceId);

然后在api 11级以上

name.addAll(YOUR_OBJECTS_COLLECTION);

或以下

 for(Class item_name: collection){
 name.add(item_name);
 }

BroadcastReceiver对象仅在调用onReceive（Context，Intent）期间有效。一旦您的代码从此函数返回，系统会认为该对象已完成且不再有效。

你应该在onReceive方法中初始化scanResult

Android arrayadapter没有指定对象

编辑：

1 个答案: