判断当前线程是否为主线程

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Looper.myLooper() == Looper.getMainLooper()

在主线程中执行代码

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new Handler(Looper.getMainLooper()).post(new Runnable() {
    @Override
    public void run() {
        // ...
    }
});

Tips:

1 . @JavascriptInterface 注解下的函数调用，执行线程并非主线程，而是 JavaBridge 线程。如果在此处执行 webView.loadUrl 以期望对 JS 回调的话，是不行的，会爆出如下错误；正确的方式应该是在主线程中执行 webView.loadUrl。

Caused by: java.lang.Throwable: A WebView method was called on thread ‘JavaBridge’. All WebView methods must be called on the same thread. (Expected Looper Looper (main, tid 1) {31303094} called on Looper (JavaBridge, tid 20613) {2e893026}, FYI main Looper is Looper (main, tid 1) {31303094})