从 Javascript 中调用 Android 方法

Question

我在 android 的 webview 中使用 geo-location 特征。使用 javascript (onload) 来调用Android 方法：

public void getLocation() {
   _context.getLocation();
}

当程序执行到以下的位置时：

public void locationUpdated(Location location) {
        NumberFormat frm = NumberFormat.getNumberInstance(new Locale("en_US"));
        // call javascript function
        webView.loadUrl("javascript:locationChangedHandler(" + frm.format (location.getLatitude()) + "," + frm.format(location.getLongitude()) + ")");
}

获得以下的异常：

03-10 01:17:06.262: ERROR/AndroidRuntime(659): FATAL EXCEPTION: Timer-1
        android.view.ViewRoot$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.
        at android.view.ViewRoot.checkThread(ViewRoot.java:2802)
        at android.view.ViewRoot.invalidateChild(ViewRoot.java:607)
        at android.view.ViewRoot.invalidateChildInParent(ViewRoot.java:633)
        at android.view.ViewGroup.invalidateChild(ViewGroup.java:2505)
        at android.view.View.invalidate(View.java:5139)
        at android.view.View.onFocusChanged(View.java:2664)
        at android.widget.TextView.onFocusChanged(TextView.java:6469)
        at android.widget.AutoCompleteTextView.onFocusChanged(AutoCompleteTextView.java:1048)
        at android.webkit.WebTextView.onFocusChanged(WebTextView.java:357)
        at android.view.View.clearFocusForRemoval(View.java:2577)
        at android.view.ViewGroup.removeViewInternal(ViewGroup.java:2188)
        at android.view.ViewGroup.removeViewInternal(ViewGroup.java:2181)
        at android.view.ViewGroup.removeView(ViewGroup.java:2129)
        at android.webkit.WebTextView.remove(WebTextView.java:583)
        at android.webkit.WebView.clearTextEntry(WebView.java:1830)
        at android.webkit.WebView.loadUrl(WebView.java:1542)
        at android.webkit.WebView.loadUrl(WebView.java:1553)
        at com.binus.MainView$1.gotLocation(MainView.java:33)
        at com.binus.GeoLocation$GetLastLocation.run(GeoLocation.java:88)
        at java.util.Timer$TimerImpl.run(Timer.java:289)

有什么方法可以从其它线程中访问UI线程？使用非UI线程上执行的 javascript (onload) 来调用Android方法吗？

如何使我的代码线程安全？

Answer 1

如果是在一个 View 中使用 post:

public void locationUpdated(final Location location) {
    post(new Runnable() {
        @Override
        public void run() {
            webView.loadUrl(...);
        }
    });
}

如果是在一个 Activity 中，把 post 换成 runOnUiThread。