Question

我想在广播接收器的响应上更新UI。我必须使用一级是MainActivity，另一种是CustomReceiver。

MainActivity.java

package com.example.broadcasttest;

import java.net.URLEncoder;
import java.util.ArrayList;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import android.app.Activity;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.content.SharedPreferences;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity {

    Button btn;
    TextView txt;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        btn = (Button)findViewById(R.id.btn);
        txt = (TextView)findViewById(R.id.txt);

        txt.setText("hi.........1");


    }

    public void abc()
    {
        txt.setText("hi.........2");
    }
}

这是我的CustomReceiver.java类。它接收到接收者的响应。

package com.example.broadcasttest;

import java.util.List;
import android.app.Activity;
import android.app.ActivityManager;
import android.app.ActivityManager.RunningTaskInfo;
import android.content.BroadcastReceiver;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.util.Log;
import android.widget.TextView;
import android.widget.Toast;

public class CustomReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {
        // TODO Auto-generated method stub
        ActivityManager am = (ActivityManager) context
                .getSystemService(Activity.ACTIVITY_SERVICE);
        String packageName = am.getRunningTasks(1).get(0).topActivity
                .getPackageName();
        if(packageName.equals("com.example.broadcasttest"))
        {



            @SuppressWarnings("deprecation")
            List<RunningTaskInfo> taskInfo = am.getRunningTasks(1);
            ComponentName componentInfo = taskInfo.get(0).topActivity;
            Log.d("activity name", "CURRENT Activity ::" + taskInfo.get(0).topActivity.getClassName()+"   Package Name :  "+componentInfo.getPackageName());

            if(packageName.equals("com.example.broadcasttest") && taskInfo.get(0).topActivity.getClassName().toString().equals("com.example.broadcasttest.MainActivity"))
            {
                String abc = context.getClass().toString();
                Toast.makeText(context, "hiiii "+abc, Toast.LENGTH_SHORT).show();
                Log.e("ghorar kochu", "checking");
//              Calling the method of main activity when my broadcast receiver gives me a response          
                MainActivity m = new MainActivity();
                m.abc();
            }
        }

    }

}

这是我的Manifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.broadcasttest"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="21" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

        <activity
            android:name=".Second"
            android:label="@string/app_name" >

        </activity>
        <receiver android:name="com.example.broadcasttest.CustomReceiver">
            <intent-filter >
                <action android:name="android.net.conn.CONNECTIVITY_CHANGE"/>
            </intent-filter>
        </receiver>
    </application>

</manifest>

当我运行应用程序并更改我的wifi模式时，这会给我一个NullPointer错误。

11-23 11:02:28.994: D/OpenGLRenderer(8396): Enabling debug mode 0
11-23 11:03:43.817: D/activity name(8396): CURRENT Activity ::com.example.broadcasttest.MainActivity   Package Name :  com.example.broadcasttest
11-23 11:03:43.824: E/ghorar kochu(8396): checking
11-23 11:03:43.866: E/hi(8396): helo
11-23 11:03:43.866: D/AndroidRuntime(8396): Shutting down VM
11-23 11:03:43.866: D/AndroidRuntime(8396): --------- beginning of crash
11-23 11:03:43.869: E/AndroidRuntime(8396): FATAL EXCEPTION: main
11-23 11:03:43.869: E/AndroidRuntime(8396): Process: com.example.broadcasttest, PID: 8396
11-23 11:03:43.869: E/AndroidRuntime(8396): java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
11-23 11:03:43.869: E/AndroidRuntime(8396):     at android.os.Handler.dispatchMessage(Handler.java:102)
11-23 11:03:43.869: E/AndroidRuntime(8396):     at android.os.Looper.loop(Looper.java:135)
11-23 11:03:43.869: E/AndroidRuntime(8396):     at android.app.ActivityThread.main(ActivityThread.java:5343)
11-23 11:03:43.869: E/AndroidRuntime(8396):     at java.lang.reflect.Method.invoke(Native Method)
11-23 11:03:43.869: E/AndroidRuntime(8396):     at java.lang.reflect.Method.invoke(Method.java:372)
11-23 11:03:43.869: E/AndroidRuntime(8396):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:907)
11-23 11:03:43.869: E/AndroidRuntime(8396):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:702)

任何人都可以告诉我如何解决此错误以及我如何更新我的UI。

Answer 1

感谢@MIke它解决了我的问题。我在活动所在的同一个类中使用广播。这样就不需要在Manifest.xml文件中初始化接收者名称了。

package com.example.broadcasttest;

import java.net.URLEncoder;
import java.util.ArrayList;  
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.app.Activity;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.content.SharedPreferences;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity {

    boolean mIsReceiverRegistered = false;
    MyBroadcastReceiver mReceiver = null;
    boolean isInternetPresent = false,isJsonLoad =false;

    Button btn;
    TextView txt;

    int upFlag = 0;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        btn = (Button)findViewById(R.id.btn);
        txt = (TextView)findViewById(R.id.txt);

        txt.setText("hi.........1");
        new JsonForTest().execute();
        btn.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                upFlag =1;
            }
        });
    }


    @Override
    protected void onResume() {

        // Other onResume() code here
        super.onResume();

        if (!mIsReceiverRegistered) {
            if (mReceiver == null)
                mReceiver = new MyBroadcastReceiver();
            registerReceiver(mReceiver, new IntentFilter("android.net.conn.CONNECTIVITY_CHANGE"));
            mIsReceiverRegistered = true;
        }

    }

    @Override    
    protected void onPause() {
        super.onPause();
        Log.e("UNREGISTER", "UNREGISTERloG");
        if (mIsReceiverRegistered) {
            unregisterReceiver(mReceiver);
            mReceiver = null;
            mIsReceiverRegistered = false;
        }

        // Other onPause() code here

    }

    private class MyBroadcastReceiver extends BroadcastReceiver {

        @Override
        public void onReceive(Context context, Intent intent) {


            Log.e("REGISTER", "REGISTERloG");
            ConnectionDetector  cd = new ConnectionDetector(getApplicationContext());
            // get Internet status
            isInternetPresent = cd.isConnectingToInternet();

            if (isInternetPresent && upFlag ==1 && isJsonLoad) {
                updateUI(intent);
            }

        }
    }

    public void updateUI(Intent intent){


        Log.e("hi", "heloo");

        txt.setText("hi.........2");
        Toast.makeText(getApplicationContext(), "1", Toast.LENGTH_SHORT).show();
    }


    class JsonForTest extends AsyncTask<Void, Void, Void> {

        private String msg = null;

        @Override
        protected void onPreExecute() {
            super.onPreExecute();

        }


        @Override
        protected Void doInBackground(Void... params) {
            return null;
        }

        @Override
        protected void onPostExecute(Void  resultaaa) {

            Log.e("hi", "helo");

            isJsonLoad = true;
        }

    }

}

这是我的connectionDetector类。

package com.example.broadcasttest;

import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;

public class ConnectionDetector {

     private Context _context;

        public ConnectionDetector(Context context){
            this._context = context;
        }

        public boolean isConnectingToInternet(){
            ConnectivityManager connectivity = (ConnectivityManager) _context.getSystemService(Context.CONNECTIVITY_SERVICE);
              if (connectivity != null) 
              {
                  NetworkInfo[] info = connectivity.getAllNetworkInfo();
                  if (info != null) 
                      for (int i = 0; i < info.length; i++) 
                          if (info[i].getState() == NetworkInfo.State.CONNECTED)
                          {
                              return true;
                          }

              }
              return false;
        }


}

在android中更新wifi的广播接收器的ul响应

1 个答案: