我基于这个demo构建了一个功能齐全的FragmentActivity。
最初（就像我的应用程序中的其他活动一样）数据正在从 UI 线程中的 SQLite加载到FragmentActivity.ListFragment.ListView中。
我已经成功地将其他两个活动（不是片段或列表活动）转换为使用IntentService从 SQLite 获取数据的ResultReceiver范例。此实例的明显区别在于，自定义ResultReceiver是在ListFragment中声明的，而不是在FragmentActivity中声明的：
public EWTRReceiver ArrayListFragmentReceiver;
问题： IntentService获取请求，提取数据但无法将数据返回到ListFragment：IntentService.rspPlayers() 中此行上的 NullPointerException：
r.send(mSignal, resultData);
我确信我错过了一些简单的东西，这会让我觉得自己像个白痴……我只需要被推向正确的方向。
以下是 (1) 从ListFragment到IntenService的调用，(2) IntentService 的onHandleIntent和 (3) IntentService中回调ListFragment的方法(rspPlayers())。
谢谢！
FragmentActivity.ListFragment.callCtlr()：
private void callCtlr(int mSignal){
if (BuildConfig.DEBUG) {
Log.i(Constants.TAG_FRGACTPLAYERS, "ArrayListFragment.callCtlr() called with signal: "+mSignal);
}
/** Intent to transmit between processes */
Intent intent = new Intent(getActivity(), CtlPlayers.class);
// declare Source of Signal
intent.putExtra("Source", ArrayListFragmentReceiver);
/** process signal to send to CtlPlayers */
switch (mSignal){
case Constants.S_DB_READPLYRLDR:
if (BuildConfig.DEBUG) {
Log.i(Constants.TAG_FRGACTPLAYERS, "ArrayListFragment.callCtlr(S_DB_READPLYRLDR) to CtlPlayers.");
}
// Send CtlAlliances the request for the list of Alliances in current Sector
intent.putExtra("CurrentSector", this.getArguments().getString("FSECTR"));
intent.putExtra("CurrentAlliance", this.getArguments().getString("FANAME"));
intent.putExtra("signal", Constants.S_DB_READPLYRLDR);
break;
case Constants.S_DB_READPLYRREC:
if (BuildConfig.DEBUG) {
Log.i(Constants.TAG_FRGACTPLAYERS, "ArrayListFragment.callCtlr(S_DB_READPLYRREC) to CtlPlayers.");
}
// Send CtlAlliances the request for the list of Alliances in current Sector
intent.putExtra("CurrentSector", this.getArguments().getString("FSECTR"));
intent.putExtra("CurrentAlliance", this.getArguments().getString("FANAME"));
intent.putExtra("signal", Constants.S_DB_READPLYRREC);
break;
default:
//do nothing
break;
}
getActivity().startService(intent);
}
IntentService.onHandleIntent():
protected void onHandleIntent(Intent intentREQ) {
if (BuildConfig.DEBUG) {
Log.i(Constants.TAG_CTLPLAYERS, "onHandleIntent(Intent intent) called.");
}
/** get the receiver and bundle from the incoming Intent */
ResultReceiver rInComing = intentREQ.getParcelableExtra("Source");
/** get the bundle from the incoming Intent */
extras = intentREQ.getExtras();
/** variable to convey results to ActDlgAddPlyr */
boolean mAnswer = false;
/** tracks ActSector's context */
Context mCtx = getApplicationContext();
int mSignal = intentREQ.getIntExtra("signal", Constants.R_NO_SIGNAL);
if (BuildConfig.DEBUG) {
Log.i(Constants.TAG_CTLPLAYERS, "Signal Received = " + mSignal);
}
switch (mSignal) {
case Constants.R_NO_SIGNAL :
if (BuildConfig.DEBUG) {
Log.i(Constants.TAG_CTLPLAYERS, "onHandleIntent(): NO READABLE SIGNAL WAS RECEIVED!");
}
break;
case Constants.S_DB_ADDPLYR :
if (BuildConfig.DEBUG) {
Log.i(Constants.TAG_CTLPLAYERS, "onHandleIntent(): S_DB_ADDPLYR received.");
}
synchronized (this) {
// Get the New Sector Name from the bundle
if (BuildConfig.DEBUG) {
Log.i(Constants.TAG_CTLPLAYERS, "onHandleIntent(): S_DB_ADDPLYR received with New Player.");
}
mAnswer = addNewPlayer(mCtx, extras);
rspPlayers(Constants.R_DB_ADDPLYR, mAnswer, rInComing);
}
break;
case Constants.S_DB_READPLYRLDR :
if (BuildConfig.DEBUG) {
Log.i(Constants.TAG_CTLPLAYERS, "onHandleIntent(): S_DB_READPLYRLDR received.");
}
synchronized (this) {
// Get the New Sector Name from the bundle
if (BuildConfig.DEBUG) {
Log.i(Constants.TAG_CTLPLAYERS, "onHandleIntent(): S_DB_READPLYRLDR received.");
}
mAnswer = readPlyrLdr(mCtx, extras);
rspPlayers(Constants.R_DB_READPLYRLDR, mAnswer, rInComing);
}
break;
case Constants.S_DB_READPLYRREC :
if (BuildConfig.DEBUG) {
Log.i(Constants.TAG_CTLPLAYERS, "onHandleIntent(): S_DB_READPLYRREC received.");
}
synchronized (this) {
// Get the New Sector Name from the bundle
if (BuildConfig.DEBUG) {
Log.i(Constants.TAG_CTLPLAYERS, "onHandleIntent(): S_DB_READPLYRREC received.");
}
mAnswer = readPlyrRec(mCtx, extras);
rspPlayers(Constants.R_DB_READPLYRREC, mAnswer, rInComing);
}
break;
} // end switch
}
IntentService.rspPlayers() [将结果发送回 FragmentActivity.ListFragment]：
private void rspPlayers(int mSignal, boolean mCode, ResultReceiver r) {
if (BuildConfig.DEBUG) {
Log.i(Constants.TAG_CTLPLAYERS, "respPlayers() called with signal, code: "+mSignal+", "+mCode);
}
Bundle resultData = new Bundle();
switch (mSignal) {
case Constants.R_DB_ADDPLYR :
if (mCode == true) {
resultData.putInt("reqStatus", Constants.R_TRUE_THAT);
} else {
resultData.putInt("reqStatus", Constants.R_NO_WAY);
}
break;
case Constants.R_DB_READPLYRLDR :
if (mCode == true) {
resultData.putInt("reqStatus", Constants.R_TRUE_THAT);
resultData.putInt("NumLdrRows", NumLdrRows);
resultData.putSerializable("LPlyrList", LPlyrArray);
} else {
resultData.putInt("reqStatus", Constants.R_NO_WAY);
}
break;
case Constants.R_DB_READPLYRREC :
if (mCode == true) {
resultData.putInt("reqStatus", Constants.R_TRUE_THAT);
resultData.putInt("NumRecRows", NumRecRows);
resultData.putSerializable("RPlyrList", RPlyrArray);
} else {
resultData.putInt("reqStatus", Constants.R_NO_WAY);
}
break;
default :
// do nothing
break;
}
try {
r.send(mSignal, resultData);
} catch (java.lang.Exception e) {
Log.e(Constants.TAG_CTLPLAYERS, "rspPlayers(): Exception message: "+e.getMessage());
Log.e(Constants.TAG_CTLPLAYERS, "rspPlayers(): Exception cause: "+e.getCause());
e.printStackTrace();
}
}