如何在Android的WebView中从javascript获取返回值?
我想从Android中的Javascript获取一个返回值。我可以用iPhone来做,但用Android不行。我使用了loadUrl,但它返回的是void而不是对象。有人能帮我吗?使用如何在Android的WebView中从javascript获取返回值?,android,return,Android,Return,我想从Android中的Javascript获取一个返回值。我可以用iPhone来做,但用Android不行。我使用了loadUrl,但它返回的是void而不是对象。有人能帮我吗?使用addJavascriptInterface()向Javascript环境添加Java对象。让您的Javascript在该Java对象上调用一个方法以提供其“返回值”。下面是一个如何实现它的技巧: 将此客户端添加到您的WebView: final class MyWebChromeClient extends We
addJavascriptInterface()
向Javascript环境添加Java对象。让您的Javascript在该Java对象上调用一个方法以提供其“返回值”。下面是一个如何实现它的技巧:
将此客户端添加到您的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;
}
}
webView.evaluateJavascript("foo.bar()", new ValueCallback<String>() {
@Override public void onReceiveValue(String value) {
// value is the result returned by the Javascript as JSON
}
});
现在在javascript调用中执行以下操作:
webView.loadUrl("javascript:alert(functionThatReturnsSomething)");
现在,在onJsAlert调用中,“message”将包含返回值。以下是我今天想到的。它是线程安全的,效率相当高,并且允许在Android WebView中从Java执行同步Javascript 适用于Android 2.2及更高版本。(需要commons lang,因为我需要将代码片段作为Javascript字符串传递给eval()。您可以通过将代码不用引号括起来,而是用
function(){}
来删除此依赖项)
首先,将其添加到Javascript文件:
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);
}
}
private Handler=new Handler();
私有最终AtomicInteger evalJsIndex=新的AtomicInteger(0);
private final Map jsReturnValues=new HashMap();
私有最终对象jsReturnValueLock=新对象();
私有网络视图;
@凌驾
创建时的公共void(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
webView=(webView)findviewbyd(R.id.webView);
addJavascriptInterface(新的MyJavascriptInterface(this),“androidInterface”);
}
公共字符串evalJs(最终字符串js){
final int index=evalJsIndex.incrementAndGet();
handler.post(新的Runnable(){
公开募捐{
loadUrl(“javascript:evalJsForAndroid(“+index+”,”+
“\”“+StringEscapeUtils.escapeEcmaScript(js)+”\”);
}
});
返回waitForJsReturnValue(索引,10000);
}
私有字符串waitForJsReturnValue(int索引,int waitMs){
长启动=System.currentTimeMillis();
while(true){
长时间运行=System.currentTimeMillis()-开始;
如果(经过>等待毫秒)
打破
已同步(jsReturnValueLock){
String value=jsReturnValues.remove(索引);
if(值!=null)
返回值;
long-toWait=waitMs-(System.currentTimeMillis()-start);
如果(等待>0)
试一试{
jsReturnValueLock.wait(等待);
}捕捉(中断异常e){
打破
}
其他的
打破
}
}
Log.e(“MyActivity”、“放弃;等待”+(waitMs/1000)+“返回值秒”+索引);
返回“”;
}
私有void processJsReturnValue(int索引,字符串值){
已同步(jsReturnValueLock){
jsReturnValues.put(索引,值);
jsReturnValueLock.notifyAll();
}
}
私有静态类MyJavascriptInterface{
私人活动;
公共MyJavascriptInterface(MyActivity活动){
这个。活动=活动;
}
//此注释在Jelly Bean及更高版本中是必需的:
@JavascriptInterface
public void processReturnValue(int索引,字符串值){
activity.processJsReturnValue(索引、值);
}
}
与Keith
相同,但答案较短
webView.addJavascriptInterface(this, "android");
webView.loadUrl("javascript:android.onData(functionThatReturnsSomething)");
并实现了该功能
@JavascriptInterface
public void onData(String value) {
//.. do something with the data
}
不要忘记从
proguard
列表中删除onData
(如果您启用了proguard)@Felix Khazin建议的解决方案是可行的,但缺少一个关键点
javascript调用应该在加载WebView
中的网页后进行。将此WebViewClient
与WebChromeClient
一起添加到WebView
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;
}
}
在API 19+上,最好的方法是调用您的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;
}
}
webView.evaluateJavascript("foo.bar()", new ValueCallback<String>() {
@Override public void onReceiveValue(String value) {
// value is the result returned by the Javascript as JSON
}
});
webView.evaluateJavascript(“foo.bar()”,new ValueCallback()){
@重写公共void onReceiveValue(字符串值){
//值是Javascript作为JSON返回的结果
}
});
更详细的相关回答:作为另一种变体,使用自定义方案与
Android原生代码HTML/JS代码
进行通信。例如,MRAID使用这种技术
main活动
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
WebView.setWebContentsDebuggingEnabled(true);
}
final WebView webview = new CustomWebView(this);
setContentView(webview);
webview.loadUrl("file:///android_asset/customPage.html");
webview.postDelayed(new Runnable() {
@Override
public void run() {
//Android -> JS
webview.loadUrl("javascript:showToast()");
}
}, 1000);
}
}
CustomWebView
public class CustomWebView extends WebView {
public CustomWebView(Context context) {
super(context);
setup();
}
@SuppressLint("SetJavaScriptEnabled")
private void setup() {
setWebViewClient(new AdWebViewClient());
getSettings().setJavaScriptEnabled(true);
}
private class AdWebViewClient extends WebViewClient {
@Override
public boolean shouldOverrideUrlLoading(WebView view, String url) {
if (url.startsWith("customschema://")) {
//parse uri
Toast.makeText(CustomWebView.this.getContext(), "event was received", Toast.LENGTH_SHORT).show();
return true;
}
return false;
}
}
}
customPage.html(位于折叠的资产中)
JavaScript视图
函数showtoots(){
window.location=“customschema://goto/";
}
您可以这样做:
[Activity(Label = "@string/app_name", Theme = "@style/AppTheme", MainLauncher = true)]
public class MainActivity : AppCompatActivity
{
public WebView web_view;
public static TextView textView;
protected override void OnCreate(Bundle savedInstanceState)
{
base.OnCreate(savedInstanceState);
Xamarin.Essentials.Platform.Init(this, savedInstanceState);
Window.AddFlags(WindowManagerFlags.Fullscreen);
Window.ClearFlags(WindowManagerFlags.ForceNotFullscreen);
// Set our view from the "main" layout resource
SetContentView (Resource.Layout.main);
web_view = FindViewById<WebView>(Resource.Id.webView);
textView = FindViewById<TextView>(Resource.Id.textView);
web_view.Settings.JavaScriptEnabled = true;
web_view.SetWebViewClient(new SMOSWebViewClient());
web_view.LoadUrl("https://stns.egyptair.com");
}
public override void OnRequestPermissionsResult(int requestCode, string[] permissions, [GeneratedEnum] Android.Content.PM.Permission[] grantResults)
{
Xamarin.Essentials.Platform.OnRequestPermissionsResult(requestCode, permissions, grantResults);
base.OnRequestPermissionsResult(requestCode, permissions, grantResults);
}
}
public class SMOSWebViewClient : WebViewClient
{
public override bool ShouldOverrideUrlLoading(WebView view, IWebResourceRequest request)
{
view.LoadUrl(request.Url.ToString());
return false;
}
public override void OnPageFinished(WebView view, string url)
{
view.EvaluateJavascript("document.getElementsByClassName('notf')[0].innerHTML;", new JavascriptResult());
}
}
public class JavascriptResult : Java.Lang.Object, IValueCallback
{
public string Result;
public void OnReceiveValue(Java.Lang.Object result)
{
string json = ((Java.Lang.String)result).ToString();
Result = json;
MainActivity.textView.Text = Result.Replace("\"", string.Empty);
}
}
[活动(标签=“@string/app_name”,Theme=“@style/AppTheme”,MainLauncher=true)]
公共类MainActivity:AppCompativeActivity
{
公共网络视图;
公共静态文本视图文本视图;
创建时受保护的覆盖无效(Bundle savedInstanceState)
{
base.OnCreate(savedInstanceState);
Xamarin.Essentials.Platform.Init(这个,savedInstanceState);
AddFlags(WindowManagerFlags.Fullscreen);
Window.ClearFlags(WindowManagerFlags.ForceNotFullscreen);
//从“主”布局资源设置视图
SetContentView(Resource.Layout.main);
web_view=findviewbyd(Resource.Id.webView);
textView=FindViewById(Resource.Id.textView);
web_view.Settings.JavaScriptEnabled=true;
SetWebViewClient(新的SMOSWebViewClient());
web_view.LoadUrl(“https://stns.egyptair.com");
}
public override void OnRequestPermissionsResult(int-requestCode,string[]permissions,[GeneratedEnum]Android.Content.PM.Permission[]grantResults)
{
Xamarin.Essentials.Platform.OnRequestPermissionsResult(请求代码、权限、GrantResult);
base.onRequestPermissions