我正在尝试在收到广播时从数据库中检索一些表条目（在这种情况下是连接变化）。
我已经将错误追踪到了 在getAllData（）方法中的SQLiteDatabase db = this.getWritableDatabase（）; 行
以下是代码：
sendMessageFromDatabase：
import android.content.Context;
import android.database.Cursor;
import android.os.Handler;
import android.util.Log;
import com.loopj.android.http.AsyncHttpClient;
import com.loopj.android.http.JsonHttpResponseHandler;
import com.loopj.android.http.RequestParams;
import com.pusher.client.Pusher;
import com.pusher.client.PusherOptions;
import com.pusher.client.channel.Channel;
import com.pusher.client.channel.SubscriptionEventListener;
import org.json.JSONObject;
import java.util.ArrayList;
import cz.msebera.android.httpclient.Header;
import static android.content.ContentValues.TAG;
public class sendMessageFromDatabase {
private static final String TAG = "SendingMFD DB";
private final Handler handler;
final String MESSAGES_ENDPOINT = "http://fragmentstanvir.azurewebsites.net";
DataBaseHelper myDB;
Context context;
public sendMessageFromDatabase(Handler handler) {
this.handler = handler;
RequestParams rp = new RequestParams();
SendMessageFromDBMethod(rp);
}
public void SendMessageFromDBMethod(RequestParams param) {
Log.d(TAG, "Method started");
AsyncHttpClient client = new AsyncHttpClient();
//pusher
PusherOptions options = new PusherOptions();
options.setCluster("ap2");
Pusher pusher = new Pusher("87ded5c4cb1e22c46dd4", 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();
RequestParams postParams = new RequestParams();
// Database
Log.d(TAG, "DATABASE OPERATIONS STARTED");
myDB = new DataBaseHelper(context);
Cursor res = myDB.getAllData();
if (res.getCount() == 0) {
Log.d(TAG, "No data found");
return;
}
final ArrayList<String> messageList = new ArrayList();
while (res.moveToNext()) {
messageList.add(res.getString(0));
}
Log.d(TAG, "BUFFER LENGTH :: " + messageList.size());
for (int i = 0; i < messageList.size(); i++) {
client.post(MESSAGES_ENDPOINT + "/messages" + messageList.get(i).toString(), postParams, new JsonHttpResponseHandler() {
@Override
public void onSuccess(int statusCode, Header[] headers, JSONObject response) {
handler.post(new Runnable() {
@Override
public void run() {
Log.d(TAG, "fuck the log");
}
});
}
@Override
public void onFailure(int statusCode, Header[] headers, String responseString, Throwable throwable) {
//Toast.makeText(, "Something went wrong :(", Toast.LENGTH_LONG).show();
}
});
}
return;
}
}
DataBaseHelper.java ::
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class DataBaseHelper extends SQLiteOpenHelper {
public static final String DATABASE_NAME = "messages.db";
public static final String TABLE_NAME = "kalol";
public static final String COL_1 = "params";
SQLiteDatabase db;
private Context mContext;
public DataBaseHelper(Context context) {
super(context, DATABASE_NAME, null, 1);
mContext = context;
db = this.getWritableDatabase();
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("create table " + TABLE_NAME + " (PARAMS TEXT UNIQUE) ");
}
@Override
public void onUpgrade(SQLiteDatabase db, int i, int i1) {
db.execSQL("DROP TABLE IF EXISTS" + TABLE_NAME);
onCreate(db);
}
public boolean insertData(String params){
SQLiteDatabase db = this.getWritableDatabase();
ContentValues contentValues = new ContentValues();
contentValues.put(COL_1,params);
long result = db.insert(TABLE_NAME,null, contentValues);
if (result == -1)
return false;
else
return true;
}
public Cursor getAllData(){
SQLiteDatabase db = this.getWritableDatabase();
Cursor res = db.rawQuery("SELECT * FROM " + TABLE_NAME, null);
return res;
}
}
Logcat：
04-06 00:17:00.999 22916-22916/com.tanvirsingh.fragmentsdemo E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.tanvirsingh.fragmentsdemo, PID: 22916
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 start receiver com.tanvirsingh.fragmentsdemo.NetworkChangeReceiver: java.lang.NullPointerException: Attempt to invoke virtual method 'android.database.sqlite.SQLiteDatabase android.content.Context.openOrCreateDatabase(java.lang.String, int, android.database.sqlite.SQLiteDatabase$CursorFactory, android.database.DatabaseErrorHandler)' on a null object reference
at android.app.ActivityThread.handleReceiver(ActivityThread.java:2778)
at android.app.ActivityThread.-wrap14(ActivityThread.java)
at android.app.ActivityThread$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$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
at de.robv.android.xposed.XposedBridge.main(XposedBridge.java:102)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.database.sqlite.SQLiteDatabase android.content.Context.openOrCreateDatabase(java.lang.String, int, android.database.sqlite.SQLiteDatabase$CursorFactory, android.database.DatabaseErrorHandler)' on a null object reference
at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:223)
at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:163)
at com.tanvirsingh.fragmentsdemo.DataBaseHelper.<init>(DataBaseHelper.java:20)
at com.tanvirsingh.fragmentsdemo.sendMessageFromDatabase.SendMessageFromDBMethod(sendMessageFromDatabase.java:73)
at com.tanvirsingh.fragmentsdemo.sendMessageFromDatabase.<init>(sendMessageFromDatabase.java:40)
at com.tanvirsingh.fragmentsdemo.NetworkChangeReceiver.onReceive(NetworkChangeReceiver.java:43)
at android.app.ActivityThread.handleReceiver(ActivityThread.java:2771)
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)