Android JavascriptInterface problem

问题

I am an Android beginner. I am trying to change a textview value in an activity in a webview javascript call to javascript interface class. There is a webview and a textview in the activity layout.

MyWebActivity

public class MyWebActivity extends Activity {
    ...
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        String url =  "http://myurl...";
        webview = (WebView) findViewById(R.id.webview);

        webview.getSettings().setJavaScriptEnabled(true);
        webview.setWebChromeClient(new WebChromeClient());
        webview.loadUrl(url);

        webview.addJavascriptInterface(new JsInterface(this), "Android");
    }
    ...
}

JsInterface.java

public class JsInterface {
        ...
       public void setUIText()
       {
             TextView textView1  = (TextView) ((Activity) mContext).findViewById(R.id.textView1);

            /*This line not work*/
        textView1.setText("Hello"); 

            /*This line work*/  
            Toast.makeText(mContext, textView1.getText(), Toast.LENGTH_SHORT).show();
       }
}

the html file

Android.setUIText();

Then problem is, when I call Android.setUIText() in the html file, it trigger the JsInterface's setUIText, and I cannot set the text for the textView1, but I can get the textView1's text using getText().

What's the reason? How can I fix it?

回答1:

You cannot do this. javascript interface run in a new thread (not in the main). So, to change your UI (the textfield owned by MyWebActivity), you need to use an handler to re-Synchronize events.

step:

create an handler in your MyWebActicity.
In javascript interface in the method that should change your textfield send an empty message to your MyWebActivity. (ex: hrefresh.sendEmptMessage(MyHandler.REFRESH_TEXTFIELD)).
manage the empty message in your handler, that will call a method in your MyWebActivity that will change the textfield

回答2:

Just add these lines in your setUIText Function

      public void setUIText()
      {
           final String msgeToast = toast + newToast;           
           myHandler.post(new Runnable() {
               @Override
               public void run() {
                   // This gets executed on the UI thread so it can safely modify Views
                   myTextView.setText(msgeToast);
               }
           });
           Toast.makeText(mContext, textView1.getText(), Toast.LENGTH_SHORT).show();
      }

回答3:

You can use

myTextView.post(...

as well.

回答4:

Try this:

final TextView textView1  = (TextView) ((Activity) mContext).findViewById(R.id.textView1);
((Activity) mContext).runOnUiThread(new Runnable() {
    @Override
    public void run() {
        textView1.setText("Hello");
    }
}

来源：https://stackoverflow.com/questions/6758604/android-javascriptinterface-problem

标签

android

user-interface

webview

textview