<input type="file" /> 选择文件并按提交按钮，一切正常。现在我需要创建一个 Android 应用程序（使用 C# 和 Mono for Android），其中包含简单的 Webview，并且必须像 Web 版本一样工作。Choose file 按钮时，文件对话框不会打开。WebChromeClient没有声明openFileChooser()方法，因此我们需要声明一个版本，称为OpenFileWebChromeClient。它声明了一个virtual OpenFileChooser方法，并为其提供了绑定，以便可以对其进行重写：using System;
using Android.App;
using Android.Content;
using Android.Runtime;
using Android.OS;
using Android.Webkit;
namespace Scratch.FileUpload
{
[Register ("android/webkit/WebChromeClient", DoNotGenerateAcw=true)]
class OpenFileWebChromeClient : WebChromeClient {
static IntPtr id_openFileChooser;
[Register ("openFileChooser", "(Landroid/webkit/ValueCallback;)V", "GetOpenFileChooserHandler")]
public virtual void OpenFileChooser (IValueCallback uploadMsg)
{
if (id_openFileChooser == IntPtr.Zero)
id_openFileChooser = JNIEnv.GetMethodID (ThresholdClass, "openFileChooser", "(Landroid/webkit/ValueCallback;)V");
if (GetType () == ThresholdType)
JNIEnv.CallVoidMethod (Handle, id_openFileChooser, new JValue (JNIEnv.ToJniHandle (uploadMsg)));
else
JNIEnv.CallNonvirtualVoidMethod (Handle, ThresholdClass, id_openFileChooser, new JValue (JNIEnv.ToJniHandle (uploadMsg)));
}
#pragma warning disable 0169
static Delegate cb_openFileChooser;
static Delegate GetOpenFileChooserHandler ()
{
if (cb_openFileChooser == null)
cb_openFileChooser = JNINativeWrapper.CreateDelegate ((Action<IntPtr, IntPtr, IntPtr>) n_OpenFileChooser);
return cb_openFileChooser;
}
static void n_OpenFileChooser (IntPtr jnienv, IntPtr native__this, IntPtr native_uploadMsg)
{
OpenFileWebChromeClient __this = Java.Lang.Object.GetObject<OpenFileWebChromeClient> (native__this, JniHandleOwnership.DoNotTransfer);
var uploadMsg = Java.Lang.Object.GetObject<IValueCallback> (native_uploadMsg, JniHandleOwnership.DoNotTransfer);
__this.OpenFileChooser (uploadMsg);
}
#pragma warning restore 0169
}
}
接下来，由于C#缺乏匿名内部类，我们需要一个显式的类，在这里命名为MyOpenFileWebChromeClient：
namespace Scratch.FileUpload {
class MyOpenFileWebChromeClient : OpenFileWebChromeClient {
Action<IValueCallback> cb;
public MyOpenFileWebChromeClient(Action<IValueCallback> cb)
{
this.cb = cb;
}
public override void OpenFileChooser (IValueCallback uploadMsg)
{
cb (uploadMsg);
}
}
Activity端口与您提到的博客文章几乎相同，只是它使用MyOpenFileWebChromeClient而不是匿名内部类。我还更新了一些逻辑以显示OnActivityResult()接收到的URI：
namespace Scratch.FileUpload {
[Activity (Label = "Scratch.FileUpload", MainLauncher = true)]
public class Activity1 : Activity
{
private WebView wv;
private IValueCallback mUploadMessage;
const int FilechooserResultcode = 1;
protected override void OnCreate (Bundle bundle)
{
base.OnCreate (bundle);
wv = new WebView (this);
wv.SetWebViewClient(new WebViewClient());
wv.SetWebChromeClient(new MyOpenFileWebChromeClient(uploadMsg => {
mUploadMessage = uploadMsg;
var intent = new Intent (Intent.ActionGetContent);
intent.AddCategory(Intent.CategoryOpenable);
intent.SetType("image/*");
StartActivityForResult(Intent.CreateChooser(intent, "File Chooser"),
FilechooserResultcode);
}));
SetHtml(null);
SetContentView(wv);
}
void SetHtml(string filename)
{
string html = @"<html>
<body>
<h1>Hello, world!</h1>
<p>Input Box:</p>
<input type=""file"" />
<p>URI: " + filename + @"
</body>
</html>";
wv.LoadData(html, "text/html", "utf-8");
}
protected override void OnActivityResult (int requestCode, Result resultCode, Intent data)
{
base.OnActivityResult (requestCode, resultCode, data);
if (requestCode == FilechooserResultcode) {
if (mUploadMessage == null)
return;
var result = data == null || resultCode != Result.Ok
? null
: data.Data;
SetHtml(result.ToString());
mUploadMessage.OnReceiveValue(result);
mUploadMessage = null;
}
}
}
}
MyOpenFileWebChromeClient存在问题，因为它不起作用，原因与M0S的博客不能在匿名内部类声明中使用@Override相同：您构建应用程序的android.jar未声明openFileChooser()方法。@Override，导致MyOpenFileWebChromeClient的Android Callable Wrapper出现问题。package scratch.fileupload;
public class MyOpenFileWebChromeClient
extends android.webkit.WebChromeClient
{
static final String __md_methods;
static {
__md_methods =
"n_openFileChooser:(Landroid/webkit/ValueCallback;)V:GetOpenFileChooserHandler\n" +
"";
mono.android.Runtime.register ("Scratch.FileUpload.MyOpenFileWebChromeClient, Scratch.FileUpload, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null", MyOpenFileWebChromeClient.class, __md_methods);
}
@Override
public void openFileChooser (android.webkit.ValueCallback p0)
{
n_openFileChooser (p0);
}
private native void n_openFileChooser (android.webkit.ValueCallback p0);
java.util.ArrayList refList;
public void monodroidAddReference (java.lang.Object obj)
{
if (refList == null)
refList = new java.util.ArrayList ();
refList.add (obj);
}
public void monodroidClearReferences ()
{
if (refList != null)
refList.clear ();
}
}
MyOpenFileWebChromeClient.openFileChooser() 上使用 @Override 会生成编译器错误，那我们该如何解决呢？通过提供自己的 @Override 注释来实现！package scratch.fileupload;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.SOURCE)
public @interface Override {
}
Override.java的文件中，将其添加到项目中，并将其构建操作设置为AndroidJavaSource。MyOpenFileWebChromeClient类型相同的包中提供了自定义的@Override注释。（这要求您知道生成的包名称，并且为您执行此操作的每个包提供单独的@Override注释。）在同一包中的类型优先于导入的名称，甚至优于来自java.lang的名称，因此我们的自定义@Override注释不仅可以编译，而且由MyOpenFileWebChromeClient Android可调用包在优先于java.lang.Override注释的情况下使用。步骤1 = 文件上传将工作，我们需要在Android清单中授予读/写权限。在MainActivity.cs中
step2=
private Action<int, Result, Intent> resultCallbackvalue;
public void StartActivity(Intent intent, int requestCode, Action<int, Result, Intent> resultCallback)
{
this.resultCallbackvalue = resultCallback;
StartActivityForResult(intent, requestCode);
}
protected override void OnActivityResult(int requestCode, Result resultCode, Intent data)
{
base.OnActivityResult(requestCode, resultCode, data);
if (this.resultCallbackvalue != null)
{
this.resultCallbackvalue(requestCode, resultCode, data);
this.resultCallbackvalue = null;
}
}
step3= add ExtendedChromeClient,cs Inheriting from : WebChromeClient
private static int filechooser = 1;
private IValueCallback message;
private MainActivity activity = null;
public ExtendedChromeClient(MainActivity context)
{
this.activity = context;
}
public override bool OnShowFileChooser(WebView webView, IValueCallback filePathCallback, FileChooserParams fileChooserParams)
{
this.message = filePathCallback;
Intent chooserIntent = fileChooserParams.CreateIntent();
chooserIntent.AddCategory(Intent.CategoryOpenable);
this.activity.StartActivity(Intent.CreateChooser(chooserIntent, "File Chooser"), filechooser, this.OnActivityResult);
return true;
}
private void OnActivityResult(int requestCode, Result resultCode, Intent data)
{
if (data != null)
{
if (requestCode == filechooser)
{
if (null == this.message)
{
return;
}
this.message.OnReceiveValue(WebChromeClient.FileChooserParams.ParseResult((int)resultCode, data));
this.message = null;
}
}
}