我已经阅读了其他存在的线程，但没有一个能够解决我的问题。
我正在构建一个应用程序，当没有互联网并将它们存储到数据库时，它会缓存邮件。这个想法是当有网络连接时，它从数据库中提取数据并在后台发送消息 - 为此我制作了一个广播接收器并使其接收“android.net.conn.CONNECTIVITY_CHANGE”广播 - 然后制作应用程序将消息发布到服务器
网络更改时收到的错误：
java.lang.RuntimeException: Unable to instantiate receiver com.tanvirsingh.fragmentsdemo.NetworkChangeReceiver: java.lang.InstantiationException: java.lang.Class<com.tanvirsingh.fragmentsdemo.NetworkChangeReceiver> has no zero argument constructor
广播接收器类（NetworkChangeReceiver.java）：
public class NetworkChangeReceiver extends BroadcastReceiver{
private static final String TAGNCR = "JSON";
private final Handler handler; // Handler used to execute code on the UI thread
public NetworkChangeReceiver(Handler handler) {
this.handler = handler;
}
DataBaseHelper myDB;
final String MESSAGES_ENDPOINT = "";
@Override
public void onReceive(Context context, Intent intent) {
int[] type = {ConnectivityManager.TYPE_MOBILE, ConnectivityManager.TYPE_WIFI};
if (isNetworkAvailable(context) == true){
//check for messages to be sent
myDB = new DataBaseHelper(context);
Cursor res = myDB.getAllData();
if (res.getCount() == 0)
{
Log.d(TAG,"No data found");
return;
}
StringBuffer buffer = new StringBuffer();
while( res.moveToNext()){
buffer.append("Params: " + res.getString(0)+ "\n");
}
Log.d(TAGNCR,buffer.toString());
return;
} else {
}
}
public void SendMessageFromDB(RequestParams param){
AsyncHttpClient client = new AsyncHttpClient();
//pusher
PusherOptions options = new PusherOptions();
options.setCluster("");
Pusher pusher = new Pusher("", options);
Channel channel = pusher.subscribe("my-channel");
channel.bind("my-event", new SubscriptionEventListener() {
@Override
public void onEvent(String channelName, String eventName, final String data) {
System.out.println(data);
}
});
pusher.connect();
final RequestParams params = param;
client.post(MESSAGES_ENDPOINT + "/messages", params, new JsonHttpResponseHandler() {
@Override
public void onSuccess(int statusCode, Header[] headers, JSONObject response) {
handler.post(new Runnable() {
@Override
public void run() {
Log.d(TAG, params.toString());
}
});
}
@Override
public void onFailure(int statusCode, Header[] headers, String responseString, Throwable throwable) {
//Toast.makeText(, "Something went wrong :(", Toast.LENGTH_LONG).show();
}
});
return;
}
//function to check if internet is available
private static boolean isNetworkAvailable(Context context){
try{
ConnectivityManager cm = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo activeNetwork = cm.getActiveNetworkInfo();
if (activeNetwork != null) { // connected to the internet and not in Airplane mode
if (activeNetwork.getType() == ConnectivityManager.TYPE_WIFI) {
// connected to wifi
Toast.makeText(context, activeNetwork.getTypeName() + " Connected", Toast.LENGTH_SHORT).show();
return true;
} else if (activeNetwork.getType() == ConnectivityManager.TYPE_MOBILE) {
// connected to the mobile data
Toast.makeText(context, activeNetwork.getTypeName() + " Connected", Toast.LENGTH_SHORT).show();
return true;
}
} else {
// not connected to the internet
Toast.makeText(context, "No internet connection available!", Toast.LENGTH_SHORT).show();
}
} catch (Exception e){
return false;
}
return false;
}
}
按要求堆栈跟踪：
04-05 16:36:29.828 3420-3420/com.tanvirsingh.fragmentsdemo E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.tanvirsingh.fragmentsdemo, PID: 3420
Theme: themes:{default=overlay:system, iconPack:com.baranovgroup.nstyle, fontPkg:com.baranovgroup.nstyle, com.android.systemui=overlay:com.baranovgroup.nstyle, com.android.systemui.navbar=overlay:system}
java.lang.RuntimeException: Unable to instantiate receiver com.tanvirsingh.fragmentsdemo.NetworkChangeReceiver: java.lang.InstantiationException: java.lang.Class<com.tanvirsingh.fragmentsdemo.NetworkChangeReceiver> has no zero argument constructor
at android.app.ActivityThread.handleReceiver(ActivityThread.java:2752)
at android.app.ActivityThread.-wrap14(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1440)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5471)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
at de.robv.android.xposed.XposedBridge.main(XposedBridge.java:102)
Caused by: java.lang.InstantiationException: java.lang.Class<com.tanvirsingh.fragmentsdemo.NetworkChangeReceiver> has no zero argument constructor
at java.lang.Class.newInstance(Native Method)
at android.app.ActivityThread.handleReceiver(ActivityThread.java:2747)
at android.app.ActivityThread.-wrap14(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1440)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5471)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
at de.robv.android.xposed.XposedBridge.main(XposedBridge.java:102)
答案 0 :(得分：4)
Broadcast Receiver与Fragment相同，并且与许多其他类相同，应该有没有参数的默认构造函数。
只需添加默认构造函数：
public NetworkChangeReceiver() {
}
之所以如此，是因为Android系统知道类及其包的名称，但对其参数一无所知。 它使用反射，类似
Class c = Class.forName(className);
YourBroadcastReceiver broadcastReceiver = (YourBroadcastReceiver)c.newInstance();
如果没有默认的constgructor，newInstance（）将生成错误。
UPD：
在您的情况下，您应该从BroadcastReceiver中删除SendMessageFromDB方法以分离类。