我在服务内部使用一个线程，它执行一些繁重的处理，我想在此处理期间更新 GUI( Activity )。为此，我将消息从线程发送到处理程序，并从处理程序更新 GUI。但问题是只有当工作线程终止时，处理程序才会收到消息，就好像消息队列被阻塞一样。 我使用服务的原因是因为即使应用程序未显示，该过程也应该继续。
应用程序的目标是通过发送预定义命令列表来测试 NFC 芯片 (ISO15693)。所以发送命令是由线程完成的，并且对于每个命令，结果被发送到处理程序。
这是我的代码:
申请
public class ISO15693Application extends Application {
...
//Handler receiving messages from Worker thread
final RunTestHandler runTestHandler = new RunTestHandler(ISO15693Application.this);
static class RunTestHandler extends Handler {
//Avoid leak with handler
//See http://stackoverflow.com/questions/11407943/this-handler-class-should-be-static-or-leaks-might-occur-incominghandler
private final WeakReference<ISO15693Application> mApplication;
RunTestHandler(ISO15693Application isoApp) {
mApplication = new WeakReference<ISO15693Application>(isoApp);
}
@Override
public void handleMessage(Message msg) {
// TODO Auto-generated method stub
super.handleMessage(msg);
ISO15693Application isoApp = mApplication.get();
switch(msg.what){
case MSG_TEST_RESULT:
NfcVResponse r = (NfcVResponse) msg.obj;
if(r != null){
Log.i(TAG, "handleMessage Thread id : " + Thread.currentThread().getId());
isoApp.onTestResult((NfcVResponse) msg.obj, msg.arg1);
}
break;
case MSG_TEST_STARTED:
isoApp.onTestStarted(msg.arg1);
break;
case MSG_TEST_TERMINATED:
isoApp.onTestTerminated();
break;
case MSG_ABORTED:
isoApp.onTestAborted();
break;
}
}
}
public void onTestResult(NfcVResponse response, int currentCommand) {
Log.i(TAG, "onTestResult. Command: " + response.getCommand().toString()
+ " Status: " + response.getStatus());
if(testResultCallback != null){
testResultCallback.onTestResult(response);
}
}
//Called when user click on "Run" button
public synchronized void runTest(HashMap<Integer, List<Byte>> testMap){
this.testMap = testMap;
//Start last test result activity
Intent intent = new Intent(getApplicationContext(), TestResultsActivity.class);
intent.setAction(ISO15693Application.INTENT_ACTION_TEST_STARTED);
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(intent);
//Start service responsible to run the test.
runTestHandler.postDelayed(new Runnable() {
@Override
public void run() {
startTestService();
}
}, 500);
}
/*
* This function will be called by ISO15693Service.Runner to run the test in another thread.
* Messages are sent to runTestHandler to indicate start, progress and end .
*/
public synchronized void _runTest() {
boolean tagLost = false;
commandList = buildTest(testMap);
int total = commandList.size();
Message startMsg = new Message();
startMsg.what = MSG_TEST_STARTED;
startMsg.arg1 = total;
runTestHandler.sendMessage(startMsg);
Log.d(TAG, "Start test Thread id: " + Thread.currentThread().getId());
for(int index = 0;index < total; index++){
NfcVCommand cmd = commandList.get(index);
NfcVResponse response = NfcVHelper.sendCommand(getNfcV(), cmd);
switch(response.getStatus()){
case NfcHelper.NFC_STATUS_OK:
Log.i(TAG, "Command sent successfully");
break;
case NfcHelper.NFC_STATUS_NO_TAG:
//Tag has been lost, try to reconnect
Log.i(TAG, "Tag has been lost, reconnect");
...
break;
case NfcHelper.NFC_STATUS_ERROR:
default:
Log.i(TAG, "Error when sent command " + response.getResponseString());
break;
}
Message msg = new Message();
msg.what = MSG_TEST_RESULT;
msg.arg1 = index;
msg.arg2 = total;
msg.obj = response;
//Update UI with last command result
runTestHandler.sendMessage(msg);
//Even if waiting a short moment to let the message queue processing
//messages are handled only when the worker thread ends.
//The only difference is in the log message :
//I/Choreographer(26709): Skipped 34 frames! The application may be doing too much work on its main thread.
//The number of Skipped frams is bigger according to time waited.
/*try {
Thread.sleep(100);
} catch (InterruptedException e1) {
}*/
//Check tag lost and user cancellation
...
}
//Add results to db
...
runTestHandler.sendEmptyMessage(MSG_TEST_TERMINATED);
}
}
服务
public class ISO15693Service extends Service {
@Override
public void onCreate() {
Log.d(TAG, "onCreate");
//Create updater thread
this.testRunner = null;
//get application to access preferences
isoApp = (ISO15693Application) getApplication();
super.onCreate();
}
@Override
public void onDestroy() {
super.onDestroy();
Log.d(TAG, "onDestroy");
if(this.testRunner != null){
this.testRunner.interrupt();
this.testRunner = null;
}
this.runFlag = false;
this.isoApp.setTestRunning(false);
}
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
Log.d(TAG, "onStartCommand");
//not already running ?
if(!this.runFlag){
try{
this.testRunner = new Runner();
this.runFlag = true;
this.isoApp.setTestRunning(true);
this.testRunner.start();
} catch(IllegalThreadStateException e){
}
}
return super.onStartCommand(intent, flags, startId);
}
@Override
public IBinder onBind(Intent intent) {
// TODO Auto-generated method stub
return null;
}
private class Runner extends Thread{
Runner(){
super("Runner class");
}
@Override
public void run() {
super.run();
ISO15693Service is = ISO15693Service.this;
ISO15693Application isoApp = (ISO15693Application) is.getApplication();
Log.d(TAG, "Runner.run() Thread id: " + Thread.currentThread().getId());
isoApp._runTest();
is.runFlag = false;
isoApp.setTestRunning(false);
}
}
}
TestResultActivity(显示结果的 Activity )
public class TestResultsActivity extends ISO15693BaseActivity
implements ISO15693Application.TestResultCallback{
...
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_test_results);
mainLayout = (LinearLayout) findViewById(R.id.resultLayout);
progressBar = (ProgressBar) findViewById(R.id.progressBar);
...
}
@Override
public void onResume() {
super.onResume();
isoApp.setTestResultCallback(this);
}
@Override
public void onPause() {
super.onPause();
//Disable callback if activity is not at foreground
isoApp.setTestResultCallback(null);
}
//Add command result to the main layout
@Override
public void onTestResult(final NfcVResponse response) {
if(mainLayout != null){
LayoutParams params = new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT);
TestResultView rv = new TestResultView(TestResultsActivity.this, response);
mainLayout.addView(rv, params);
}
progressBar.setProgress(progress++);
}
@Override
public void onTestStarted() {
Log.i(TAG, "onTestStarted");
Log.d(TAG, "GUI Thread id: " + Thread.currentThread().getId());
mainLayout.removeAllViews();
progress = 0;
progressBar.setVisibility(View.VISIBLE);
progressBar.setMax(isoApp.getTestInfo().nbCommands);
}
@Override
public void onTestTerminated() {
Log.i(TAG, "onTestTerminated");
progressBar.setVisibility(View.GONE);
}
}
这是日志，我们可以看到“handleMessage”和“onTestResult”仅在最后一次“sendCommand”调用之后才被调用。但它们应该被直接处理，或者可能有一个小的延迟，但不能像现在这样延迟。请注意，消息发送到处理程序的时刻对应于日志中的“命令发送成功”或“发送命令时出错...”行。
还有消息“跳过 34 帧!应用程序可能在其主线程上做了太多工作。”我认为问题出在这里，此消息表明 GUI 在 34 帧期间已被卡住。但我不明白为什么，因为所有“繁重的处理”都是在另一个线程(id 69595)而不是 GUI 线程中完成的。我还尝试在每个命令处理之间等待(100-1000 毫秒)，但这没有任何改变，只是跳过了更多的“帧”。
12-16 10:43:19.600: I/ISO15693Application(26709): Activity TestResultsActivity created
12-16 10:43:19.615: D/TestResultsActivity(26709): GUI Thread id: 1
12-16 10:43:20.145: D/ISO15693Service(26709): onCreate
12-16 10:43:20.145: D/ISO15693Service(26709): onStartCommand
12-16 10:43:20.145: D/ISO15693Application(26709): Build Test Thread id: 69595
12-16 10:43:20.150: I/ISO15693Application(26709): Test started: 8 commands
12-16 10:43:20.150: I/TestResultsActivity(26709): onTestStarted
12-16 10:43:20.150: D/TestResultsActivity(26709): GUI Thread id: 1
12-16 10:43:20.150: D/ISO15693Application(26709): Start test Thread id: 69595
12-16 10:43:20.150: D/NfcVHelper(26709): SendCommand Thread id: 69595
12-16 10:43:20.150: D/NfcVHelper(26709): Send command : 00 20 10
12-16 10:43:20.185: D/NfcVHelper(26709): Response : 00 5a a5 5a a5
12-16 10:43:20.185: I/ISO15693Application(26709): Command sent successfully
12-16 10:43:20.185: D/NfcVHelper(26709): SendCommand Thread id: 69595
12-16 10:43:20.185: D/NfcVHelper(26709): Send command : 00 21 10 5a a5 5a a5
12-16 10:43:20.245: D/NfcVHelper(26709): Response : 00
12-16 10:43:20.245: I/ISO15693Application(26709): Command sent successfully
12-16 10:43:20.245: D/NfcVHelper(26709): SendCommand Thread id: 69595
12-16 10:43:20.245: D/NfcVHelper(26709): Send command : 00 23 01 02
12-16 10:43:20.290: D/NfcVHelper(26709): Response : 00 00 00 00 00 00 00 00 00 00 00 00 00
12-16 10:43:20.290: I/ISO15693Application(26709): Command sent successfully
12-16 10:43:20.290: D/NfcVHelper(26709): SendCommand Thread id: 69595
12-16 10:43:20.290: D/NfcVHelper(26709): Send command : 00 27 af
12-16 10:43:20.330: D/NfcVHelper(26709): Response : 00
12-16 10:43:20.330: I/ISO15693Application(26709): Command sent successfully
12-16 10:43:20.330: D/NfcVHelper(26709): SendCommand Thread id: 69595
12-16 10:43:20.330: D/NfcVHelper(26709): Send command : 00 29 d5
12-16 10:43:20.375: D/NfcVHelper(26709): Response : 00
12-16 10:43:20.375: I/ISO15693Application(26709): Command sent successfully
12-16 10:43:20.375: D/NfcVHelper(26709): SendCommand Thread id: 69595
12-16 10:43:20.375: D/NfcVHelper(26709): Send command : 00 2b
12-16 10:43:20.410: D/NfcVHelper(26709): Response : 00 xx xx xx xx xx xx xx xx xx xx xx xx xx xx
12-16 10:43:20.410: I/ISO15693Application(26709): Command sent successfully
12-16 10:43:20.410: D/NfcVHelper(26709): SendCommand Thread id: 69595
12-16 10:43:20.410: D/NfcVHelper(26709): Send command : 00 2c 00 00
12-16 10:43:20.450: D/NfcVHelper(26709): Response : 00 01
12-16 10:43:20.450: I/ISO15693Application(26709): Command sent successfully
12-16 10:43:20.450: D/NfcVHelper(26709): SendCommand Thread id: 69595
12-16 10:43:20.450: D/NfcVHelper(26709): Send command : 00 a5 16
12-16 10:43:20.505: W/System.err(26709): android.nfc.TagLostException: Tag was lost.
12-16 10:43:20.505: W/System.err(26709): at android.nfc.TransceiveResult.getResponseOrThrow(TransceiveResult.java:48)
12-16 10:43:20.505: W/System.err(26709): at android.nfc.tech.BasicTagTechnology.transceive(BasicTagTechnology.java:151)
12-16 10:43:20.505: W/System.err(26709): at android.nfc.tech.NfcV.transceive(NfcV.java:115)
12-16 10:43:20.505: W/System.err(26709): at em.marin.nfc.NfcVHelper.sendCommand(NfcVHelper.java:283)
12-16 10:43:20.505: W/System.err(26709): at em.marin.iso15693test.ISO15693Application._runTest(ISO15693Application.java:447)
12-16 10:43:20.505: W/System.err(26709): at em.marin.iso15693test.ISO15693Service$Runner.run(ISO15693Service.java:88)
12-16 10:43:20.505: I/ISO15693Application(26709): Error when sent command IO Exception occured during transmission of the command
12-16 10:43:20.730: I/Choreographer(26709): Skipped 34 frames! The application may be doing too much work on its main thread.
12-16 10:43:20.795: I/ISO15693Application(26709): handleMessage Thread id : 1
12-16 10:43:20.795: I/ISO15693Application(26709): onTestResult. Command: Read Single Block Status: 0
12-16 10:43:20.820: I/ISO15693Application(26709): handleMessage Thread id : 1
12-16 10:43:20.820: I/ISO15693Application(26709): onTestResult. Command: Write Single Block Status: 0
12-16 10:43:20.830: I/ISO15693Application(26709): handleMessage Thread id : 1
12-16 10:43:20.830: I/ISO15693Application(26709): onTestResult. Command: Read Multiple Blocks Status: 0
12-16 10:43:20.845: I/ISO15693Application(26709): handleMessage Thread id : 1
12-16 10:43:20.845: I/ISO15693Application(26709): onTestResult. Command: Write AFI Status: 0
12-16 10:43:20.855: I/ISO15693Application(26709): handleMessage Thread id : 1
12-16 10:43:20.855: I/ISO15693Application(26709): onTestResult. Command: Write DSFI Status: 0
12-16 10:43:20.865: I/ISO15693Application(26709): handleMessage Thread id : 1
12-16 10:43:20.865: I/ISO15693Application(26709): onTestResult. Command: Get System Information Status: 0
12-16 10:43:20.875: I/ISO15693Application(26709): handleMessage Thread id : 1
12-16 10:43:20.875: I/ISO15693Application(26709): onTestResult. Command: Get Multiple Block Security Status Status: 0
12-16 10:43:20.885: I/ISO15693Application(26709): handleMessage Thread id : 1
12-16 10:43:20.885: I/ISO15693Application(26709): onTestResult. Command: Read Sig Status: 1
12-16 10:43:20.890: I/ISO15693Application(26709): Test has been terminated successfully
12-16 10:43:20.890: I/TestResultsActivity(26709): onTestTerminated
12-16 10:43:20.955: D/ISO15693Service(26709): onDestroy
我希望我的解释很清楚。应用程序的体系结构可能看起来很奇怪，但我尽量将 GUI 和处理分开。当然，欢迎提出任何改进或更好实践的建议。
我在这个论坛和其他论坛上搜索了很长时间以找到类似的问题，但我没有找到，所以如果这个问题已经被问到，我提前道歉。也为我的英语感到抱歉，那不是我的母语。
最佳答案
从 _runTest() 方法中删除 synchronized 关键字。您正在同步整个 Application 对象，它似乎会阻塞 UI 线程，直到您完成 _runTest() 方法，通过for 循环。
您发布的Application 类代码中的方法不需要同步。这适用于 runTest()，尤其是 _runTest()(buildTest(testMap) 它是一个私有(private)方法，很可能只能从 _runTest()，对吧？)。
关于Android:处理程序的消息在工作线程结束时延迟，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/20614024/