我在我的應(yīng)用程序中打開一個(gè)新片段，我想計(jì)算價(jià)格并每秒打印一次（通過 asyncTask），但是當(dāng)我運(yùn)行應(yīng)用程序時(shí)停止工作。你能幫我找出問題嗎？public class RandomDrive extends Fragment {private Chronometer chronometer;private Button start;private Button stop;private TextView price;@Nullable@Overridepublic View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) { View v = inflater.inflate(R.layout.fragment_random_drive, container, false); chronometer = (Chronometer) v.findViewById(R.id.chronometer); price = v.findViewById(R.id.see_price); class SyncTaskCounter extends AsyncTask<Void, Void, Void> { @Override protected Void doInBackground(Void... voids) { double price = 0; while (!isCancelled()) { price = price + 0.05; try { Thread.sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); } printPrice(price); } return null; } @Override protected void onCancelled() { super.onCancelled(); } } final SyncTaskCounter asyncTaskCount; asyncTaskCount = new SyncTaskCounter(); start = (Button) v.findViewById(R.id.start); start.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View view) { chronometer.setBase(SystemClock.elapsedRealtime()); chronometer.start(); asyncTaskCount.execute(); } }); stop = (Button) v.findViewById(R.id.stop); stop.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View view) { chronometer.stop(); asyncTaskCount.cancel(true); } }); return v;}public void printPrice(double price1) { price.setText("the price is: " + price1 + " shekel");}}問題出在 asyncTask 中，因?yàn)楫?dāng)我在沒有 asyncTask 的情況下運(yùn)行該函數(shù)并僅在最后計(jì)算價(jià)格時(shí) - 應(yīng)用程序運(yùn)行。
1 回答
繁星coding
TA貢獻(xiàn)1797條經(jīng)驗(yàn) 獲得超4個(gè)贊
在 Android 上，您必須在 UI 線程上運(yùn)行所有 UI 代碼。AsyncTask 中的代碼在其他線程中執(zhí)行，因此它不能調(diào)用 UI 方法。
為此，您應(yīng)該使用 Handler（代碼將在 UI 線程中調(diào)用）： https ://developer.android.com/reference/android/os/Handler
final Handler h=new Handler();
h.postDelayed(new Runnable() {
public void run() {
printPrice(price);
price = price + 0.05;
h.postDelayed(this, 1000); // call for next update
}
}, 1000);
我你必須使用 AsyncTask，那么你應(yīng)該從方法更新 UI：onProgressUpdate https://developer.android.com/reference/android/os/AsyncTask
class SyncTaskCounter extends AsyncTask<Void, Double, Void> {
@Override
protected Void doInBackground(Void... voids) {
double price = 0;
while (!isCancelled()) {
price = price + 0.05;
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
publishProgress(price); // this instructs to call onProgressUpdate from UI thread.
}
return null;
}
@Override
protected void onProgressUpdate(Double... price) {
printPrice(price[0]); // this is called on UI thread
}
@Override
protected void onCancelled() {
super.onCancelled();
}
}
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