如何从android的webview中获取javascript的返回值？

Question

我想从Android中的Javascript获取返回值.我可以用iPhone做到这一点,但我不能用Android.我使用了loadUrl,但它返回的是void而不是object.有谁能够帮我？谢谢.

Answer 1

与Keith更短的答案相同

webView.addJavascriptInterface(this, "android");
webView.loadUrl("javascript:android.onData(functionThatReturnsSomething)");

并实现该功能

@JavascriptInterface
public void onData(String value) {
   //.. do something with the data
}

不要忘了删除onData从proguard列表(如果启用的ProGuard)

Answer 2

这是一个关于如何实现它的黑客攻击:

将此客户端添加到WebView:

final class MyWebChromeClient extends WebChromeClient {
        @Override
        public boolean onJsAlert(WebView view, String url, String message, JsResult result) {
            Log.d("LogTag", message);
            result.confirm();
            return true;
        }
    }

现在在你的javascript调用中执行:

webView.loadUrl("javascript:alert(functionThatReturnsSomething)");

现在在onJsAlert调用"message"中将包含返回的值.

Answer 3

使用addJavascriptInterface()Java对象添加到JavaScript环境.让您的Javascript调用该Java对象上的方法来提供其"返回值".

Answer 4

这就是我今天想出的.它是线程安全的,合理有效的,并允许从Java WebView查看同步Javascript执行.

适用于Android 2.2及更高版本.(需要commons-lang,因为我需要将我的代码片段作为Javascript字符串传递给eval().您可以通过将代码包装在引号中来删除此依赖关系,但是在中function(){})

首先,将其添加到您的Javascript文件中:

function evalJsForAndroid(evalJs_index, jsString) {
    var evalJs_result = "";
    try {
        evalJs_result = ""+eval(jsString);
    } catch (e) {
        console.log(e);
    }
    androidInterface.processReturnValue(evalJs_index, evalJs_result);
}

然后,将其添加到您的Android活动中:

private Handler handler = new Handler();
private final AtomicInteger evalJsIndex = new AtomicInteger(0);
private final Map<Integer, String> jsReturnValues = new HashMap<Integer, String>();
private final Object jsReturnValueLock = new Object();
private WebView webView;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    webView = (WebView) findViewById(R.id.webView);
    webView.addJavascriptInterface(new MyJavascriptInterface(this), "androidInterface");
}

public String evalJs(final String js) {
    final int index = evalJsIndex.incrementAndGet();
    handler.post(new Runnable() {
        public void run() {
            webView.loadUrl("javascript:evalJsForAndroid(" + index + ", " +
                                    "\"" + StringEscapeUtils.escapeEcmaScript(js) + "\")");
        }
    });
    return waitForJsReturnValue(index, 10000);
}

private String waitForJsReturnValue(int index, int waitMs) {
    long start = System.currentTimeMillis();

    while (true) {
        long elapsed = System.currentTimeMillis() - start;
        if (elapsed > waitMs)
            break;
        synchronized (jsReturnValueLock) {
            String value = jsReturnValues.remove(index);
            if (value != null)
                return value;

            long toWait = waitMs - (System.currentTimeMillis() - start);
            if (toWait > 0)
                try {
                    jsReturnValueLock.wait(toWait);
                } catch (InterruptedException e) {
                    break;
                }
            else
                break;
        }
    }
    Log.e("MyActivity", "Giving up; waited " + (waitMs/1000) + "sec for return value " + index);
    return "";
}

private void processJsReturnValue(int index, String value) {
    synchronized (jsReturnValueLock) {
        jsReturnValues.put(index, value);
        jsReturnValueLock.notifyAll();
    }
}

private static class MyJavascriptInterface {
    private MyActivity activity;

    public MyJavascriptInterface(MyActivity activity) {
        this.activity = activity;
    }

    // this annotation is required in Jelly Bean and later:
    @JavascriptInterface
    public void processReturnValue(int index, String value) {
        activity.processJsReturnValue(index, value);
    }
}

Answer 5

@Felix Khazin建议的解决方案有效,但有一个关键点缺失.

应该在WebView加载网页后进行javascript调用.将此添加WebViewClient到WebView,以及WebChromeClient.

完整示例:

@Override
public void onCreate(Bundle savedInstanceState) {
    ...
    WebView webView = (WebView) findViewById(R.id.web_view);
    webView.getSettings().setJavaScriptEnabled(true);
    webView.setWebViewClient(new MyWebViewClient());
    webView.setWebChromeClient(new MyWebChromeClient());
    webView.loadUrl("http://example.com");
}

private class MyWebViewClient extends WebViewClient {
    @Override
    public void onPageFinished (WebView view, String url){
        view.loadUrl("javascript:alert(functionThatReturnsSomething())");
    }
    @Override
    public boolean shouldOverrideUrlLoading(WebView view, String url) {
        return false;
    }
}

private class MyWebChromeClient extends WebChromeClient {
@Override
public boolean onJsAlert(WebView view, String url, String message, JsResult result) {
    Log.d("LogTag", message);
        result.confirm();
        return true;
    }
}

Answer 6

在API 19+，要做到这一点的最好方法是调用evaluateJavascript您的WebView：

webView.evaluateJavascript("foo.bar()", new ValueCallback<String>() {
    @Override public void onReceiveValue(String value) {
        // value is the result returned by the Javascript as JSON
    }
});

更详细的相关答案：https : //stackoverflow.com/a/20377857