问题描述
我想在同一本地网络上的两个 Android 设备之间建立连接，并通过我的 android 应用程序在它们之间交换数据。 为了达到这个目的，我将 Wifi Direct Api 与广播接收器方法一起使用，但由于某种原因，discoverPeers 方法没有被触发。
这是我的 MainActivity 的代码：
public class MainActivity extends AppCompatActivity {
private static MainActivity instance;
Button btnOnOff,btndiscover,btnSend;
ListView listView;
TextView read_msg_Box,connection_status;
EditText writeMessage;
WifiManager wifiManager;
wifip2pManager mManager;
wifip2pManager.Channel mChannel;
broadcastReceiver mReceiver;
IntentFilter mIntentFilter;
List<wifip2pDevice> peers = new ArrayList<wifip2pDevice>();
String[] deviceNameArray;
wifip2pDevice[] deviceArray;
wifip2pManager.PeerListListener peerListListener = new wifip2pManager.PeerListListener() {
@Override
public void onPeersAvailable(wifip2pDeviceList peerList) {
if (!peerList.getDeviceList().equals(peers)) {
peers.clear();
peers.addAll(peerList.getDeviceList());
deviceNameArray = new String[peerList.getDeviceList().size()];
deviceArray = new wifip2pDevice[peerList.getDeviceList().size()];
int index = 0;
for (wifip2pDevice device : peerList.getDeviceList()) {
deviceNameArray[index] = device.deviceName;
deviceArray[index] = device;
index++;
}
ArrayAdapter<String> adapter = new ArrayAdapter<String>(getApplicationContext(),android.R.layout.simple_list_item_1,deviceNameArray);
listView.setAdapter(adapter);
}
if (peers.size() == 0) {
Toast.makeText(getApplicationContext(),"No device Found",Toast.LENGTH_SHORT).show();
return;
}
}
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initialWork();
exqListener();
}
public static MainActivity getInstance() {
return instance;
}
private void exqListener() {
btnOnOff.setonClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (wifiManager.isWifiEnabled() == true) {
wifiManager.setWifiEnabled(false);
btnOnOff.setText("Set To OFF ");
} else {
wifiManager.setWifiEnabled(true);
btnOnOff.setText("Set To ON");
}
}
});
btndiscover.setonClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (ActivityCompat.checkSelfPermission(getApplicationContext(),Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
// Todo: Consider calling
// ActivityCompat#requestPermissions
// here to request the missing permissions,and then overriding
// public void onRequestPermissionsResult(int requestCode,String[] permissions,// int[] grantResults)
// to handle the case where the user grants the permission. See the documentation
// for ActivityCompat#requestPermissions for more details.
return;
}
mManager.discoverPeers(mChannel,new wifip2pManager.ActionListener() {
@Override
public void onSuccess() {
connection_status.setText("discovery Started");
}
@Override
public void onFailure(int reason) {
connection_status.setText("discovery Starting Failed");
}
});
}
});
}
private void initialWork() {
btnOnOff = (Button) findViewById(R.id.onOff);
btndiscover = (Button) findViewById(R.id.discover);
btnSend = (Button) findViewById(R.id.sendButton);
read_msg_Box = (TextView) findViewById(R.id.readMsg);
connection_status = (TextView) findViewById(R.id.connectionStatus);
writeMessage = (EditText) findViewById(R.id.writeMsg);
listView = (ListView) findViewById(R.id.peerListView);
wifiManager = (WifiManager) getApplicationContext().getSystemService(Context.WIFI_SERVICE);
mManager = (wifip2pManager) getSystemService(Context.WIFI_P2P_SERVICE);
mChannel = mManager.initialize(this,getMainLooper(),null);
mReceiver = new WifiDirectbroadcastReceiver(mManager,mChannel,this);
mIntentFilter = new IntentFilter();
mIntentFilter.addAction(wifip2pManager.WIFI_P2P_STATE_CHANGED_ACTION);
mIntentFilter.addAction(wifip2pManager.WIFI_P2P_PEERS_CHANGED_ACTION);
mIntentFilter.addAction(wifip2pManager.WIFI_P2P_CONNECTION_CHANGED_ACTION);
mIntentFilter.addAction(wifip2pManager.WIFI_P2P_THIS_DEVICE_CHANGED_ACTION);
}
@Override
protected void onResume() {
super.onResume();
registerReceiver(mReceiver,mIntentFilter);
}
@Override
protected void onPause() {
super.onPause();
unregisterReceiver(mReceiver);
}
}
这是 WifiDirectbroadcatReceiver 之一：
public class WifiDirectbroadcastReceiver extends broadcastReceiver {
private wifip2pManager mManager;
private wifip2pManager.Channel mChannel;
private AppCompatActivity mActivity;
public WifiDirectbroadcastReceiver(wifip2pManager mManager,wifip2pManager.Channel mChannel,AppCompatActivity mActivity) {
this.mManager = mManager;
this.mChannel = mChannel;
this.mActivity = mActivity;
}
@Override
public void onReceive(Context context,Intent intent) {
String action = intent.getAction();
if (wifip2pManager.WIFI_P2P_STATE_CHANGED_ACTION.equals(action)) {
int state = intent.getIntExtra(wifip2pManager.EXTRA_WIFI_STATE,-1);
if (state == wifip2pManager.WIFI_P2P_STATE_ENABLED) {
Toast.makeText(context,"Wifi is ON",Toast.LENGTH_SHORT).show();
} else {
Toast.makeText(context,"Wifi is OFF",Toast.LENGTH_SHORT).show();
}
} else if (wifip2pManager.WIFI_P2P_PEERS_CHANGED_ACTION.equals(action)) {
Toast.makeText(context,"Dkhal hnaya bro",Toast.LENGTH_SHORT).show();
if (mManager != null) {
if (ActivityCompat.checkSelfPermission(context,// int[] grantResults)
// to handle the case where the user grants the permission. See the documentation
// for ActivityCompat#requestPermissions for more details.
return;
}
mManager.requestPeers(mChannel,MainActivity.getInstance().peerListListener);
}
} else if(wifip2pManager.WIFI_P2P_CONNECTION_CHANGED_ACTION.equals(action)) {
// Do something
} else if (wifip2pManager.WIFI_P2P_THIS_DEVICE_CHANGED_ACTION.equals(action)) {
// Do something
}
}
}
这是 AndroidManifest.xml 中的权限：
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE"></uses-permission>
<uses-permission android:name="android.permission.CHANGE_WIFI_STATE"></uses-permission>
<uses-permission android:name="android.permission.CHANGE_NETWORK_STATE"></uses-permission>
<uses-permission android:name="android.permission.CHANGE_WIFI_STATE"></uses-permission>
<uses-permission android:name="android.permission.INTERNET"></uses-permission>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"></uses-permission>
根据代码，有一个 textView 在我按下按钮 btndiscover 后应该更改其文本，但是当我这样做时，什么也没有发生。
知道我在运行应用程序之前打开了定位服务，会出现什么错误？
解决方法
从 Android 11 开始，某些权限必须为 requested during runtime，无论您的清单中定义了什么。正如代码中的注释所指出的，您应该在 MainActivity 中使用 requestPermissions 来执行此操作，并（可选）使用 onRequestPermissionsResult 对结果做出反应。