作者热门文章
- html - 出于某种原因,IE8 对我的 Sass 文件中继承的 html5 CSS 不友好?
- JMeter 在响应断言中使用 span 标签的问题
- html - 在 :hover and :active? 上具有不同效果的 CSS 动画
- html - 相对于居中的 html 内容固定的 CSS 重复背景?
package in.webxstudio.filesharing;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.IntentFilter;
import android.net.wifi.p2p.WifiP2pManager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
public class MainActivity extends AppCompatActivity {
private static final String TAG = "MainActivity";
private WifiP2pManager manager;
private WifiP2pManager.Channel channel;
private BroadcastReceiver broadcastReceiver;
private IntentFilter mIntentFilter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
manager=(WifiP2pManager) getSystemService(Context.WIFI_P2P_SERVICE);
Log.d(TAG, "onCreate: manager "+manager);
manager.initialize(this,getMainLooper(),null);
channel=manager.initialize(this,getMainLooper(),null);
broadcastReceiver=new WiFiDirectBroadcastReceiver(manager,channel,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);
manager.discoverPeers(channel, new WifiP2pManager.ActionListener() {
@Override
public void onSuccess() {
Log.d(TAG, "onSuccess: Peered Discovered");
}
@Override
public void onFailure(int reasonCode) {
Log.d(TAG, "onFailure: Failure Discovering Peers Status Code "+reasonCode);
}
});
}
/* register the broadcast receiver with the intent values to be matched */
@Override
protected void onResume() {
super.onResume();
registerReceiver(broadcastReceiver, mIntentFilter);
}
/* unregister the broadcast receiver */
@Override
protected void onPause() {
super.onPause();
unregisterReceiver(broadcastReceiver);
}
}
我在第 3 行收到错误,如下所示。
05-27 20:59:23.807 9498-9498/in.webxstudio.filesharing E/AndroidRuntime: FATAL EXCEPTION: main
Process: in.webxstudio.filesharing, PID: 9498
java.lang.RuntimeException: Unable to start activity ComponentInfo{in.webxstudio.filesharing/in.webxstudio.filesharing.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.net.wifi.p2p.WifiP2pManager$Channel android.net.wifi.p2p.WifiP2pManager.initialize(android.content.Context, android.os.Looper, android.net.wifi.p2p.WifiP2pManager$ChannelListener)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2778)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856)
at android.app.ActivityThread.-wrap11(Unknown Source:0)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1589)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6494)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.net.wifi.p2p.WifiP2pManager$Channel android.net.wifi.p2p.WifiP2pManager.initialize(android.content.Context, android.os.Looper, android.net.wifi.p2p.WifiP2pManager$ChannelListener)' on a null object reference
at in.webxstudio.filesharing.MainActivity.onCreate(MainActivity.java:28)
我的代码有什么问题?
最佳答案
对于有同样问题的人。请确保您正在使用真实的 Android 设备而不是模拟器运行该项目。
关于java - 如何初始化 WifiP2pmanager.channel?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/50553811/
我是一名优秀的程序员,十分优秀!