Question

任何人都可以解释一下，runOnUiThread会创建新线程吗？或者它将适用于当前线程

someActivity.runOnUiThread(new Runnable() {
        @Override
        public void run() {
        }
});

Answer 1

不，它不会创建任何新线程。您指定的操作将在应用程序的UI线程上运行。您可以从其他线程（后台线程）发布操作以在UI线程上运行。（比如更新您必须在UI线程上执行的视图等）。

https://developer.android.com/reference/android/app/Activity.html#runOnUiThread(java.lang.Runnable)

Answer 2

您的UI-Thread始终在运行。此方法只在您现有的UI-Thread上运行。因此，不会创建任何线程。

Answer 3

我使用sleep函数测试它，日志显示它是同一个线程。

coalesce1a <- function(...) {
    ans <- ..1
    for (elt in list(...)[-1]) {
        i <- which(is.na(ans))
        ans[i] <- elt[i]
    }
    ans
}

setDT(d1)
setDT(d2)

#melt into long formats and full outer join the 2
mdt <- merge(melt(d1, id.vars="id"), melt(d2, id.vars="id"), by=c("id","variable"), all=TRUE)

#perform a coalesce on vectors
mdt[, value := do.call(coalesce1a, .SD), .SDcols=grep("value", names(mdt), value=TRUE)]

#pivot into original format and subset to those in d1
dcast.data.table(mdt, id ~ variable, value.var="value")[
    d1, .SD, on=.(id)]

线程中的Toast使用runOnUiThread：

05-31 08:47:06.481 6538-6538/com.example.languoguang.welcomeapp I/MainActivity: onPause: 
05-31 08:47:07.888 6538-6538/com.example.languoguang.welcomeapp I/MainActivity: onStop: 
05-31 08:47:07.893 6538-6538/com.example.languoguang.welcomeapp I/MainActivity: onDestroy: 
05-31 08:47:10.294 6538-6538/com.example.languoguang.welcomeapp I/MainActivity: run: in
05-31 08:47:25.315 6538-6538/com.example.languoguang.welcomeapp I/MainActivity: run: out
05-31 08:47:25.362 6538-6538/com.example.languoguang.welcomeapp I/MainActivity: onStart: 
05-31 08:47:25.366 6538-6538/com.example.languoguang.welcomeapp I/MainActivity: onResume:

添加，runOnUiThread签名：

@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
    try {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        TextView textView = $(R.id.main_text);
        if (textView != null) {
            textView.setOnClickListener(this);
        }
        initializeStartButton();
        initializeSetButton();

        runOnUiThread(new Runnable() {
            @Override
            public void run() {

                try {
                    Log.i(TAG, "run: in");
                    Thread.sleep(15000);
                    Toast.makeText(getBaseContext(), "Thread", Toast.LENGTH_LONG).show();
                    Log.i(TAG, "run: out");
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        });
    } catch (Exception e) {
        Log.e(MainActivity.TAG, "onCreate: ", e);
    }
}

runOnUiThread将在android中创建新线程

3 个答案: