WebView内置方案主要是通过重写WebChromeClient 来实现的，如下面的代码所示。

基本思想也很简单：通过WebChromeClient的方法以startActivityForResult的方式打开系统的文件选择器，选择文件后在onActivityResult中将结果回传给Webview即可。

当你的App最低支持版本为Android5.0及以上就很简单了，只要重写WebChromeClient 中的 onShowFileChooser()的方法即可。但是如果是5.0以下，那么还需要提供几个适配的方法，如下面的代码所示。

public class WebviewFileChooserAct extends AppCompatActivity{
private static final int REQUEST_CODE_FILE_CHOOSER = 1;

private ValueCallback<Uri> mUploadCallbackForLowApi;
private ValueCallback<Uri[]> mUploadCallbackForHighApi;

private WebView mWebView;
private WebChromeClient myWebChromeClient = new WebChromeClient() {
@TargetApi(Build.VERSION_CODES.LOLLIPOP)
@Override
public boolean onShowFileChooser(WebView webView, ValueCallback<Uri[]> filePathCallback, FileChooserParams fileChooserParams) {
mUploadCallbackForHighApi = filePathCallback;
Intent intent = fileChooserParams.createIntent();
intent.addCategory(Intent.CATEGORY_OPENABLE);
try {
startActivityForResult(intent, REQUEST_CODE_FILE_CHOOSER);
} catch (ActivityNotFoundException e) {
mUploadCallbackForHighApi = null;
Toast.makeText(EShopAiCustomServiceAct.this, R.string.cant_open_file_chooser, Toast.LENGTH_LONG).show();
return false;
}
return true;
}

// For 3.0+
protected void openFileChooser(ValueCallback<Uri> uploadMsg, String acceptType) {
openFilerChooser(uploadMsg);
}

//For Android 4.1+
protected void openFileChooser(ValueCallback<Uri> uploadMsg, String acceptType, String capture) {
openFilerChooser(uploadMsg);
}
};

private WebViewClient myWebViewClient = new WebViewClient() {
@Override
public void onReceivedError(WebView view, int errorCode, String description, String failingUrl) {
super.onReceivedError(view, errorCode, description, failingUrl);
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
return;
}
//Web页面加载失败
}

@TargetApi(Build.VERSION_CODES.M)
@Override
public void onReceivedError(WebView view, WebResourceRequest request, WebResourceError error) {
super.onReceivedError(view, request, error);
if (request.isForMainFrame()) {
//Web页面加载失败
}
}
};

@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_market_ai_custom_service);
mWebView = findViewById(R.id.webview);
configWebView(mWebView);
mWebView.loadUrl("you webpage url");
}

@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
if (requestCode == REQUEST_CODE_FILE_CHOOSER && (resultCode == RESULT_OK || resultCode == RESULT_CANCELED)) {
afterFileChooseGoing(resultCode, data);
}
}

private void afterFileChooseGoing(int resultCode, Intent data) {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
if (mUploadCallbackForHighApi == null) {
return;
}
mUploadCallbackForHighApi.onReceiveValue(WebChromeClient.FileChooserParams.parseResult(resultCode, data));
mUploadCallbackForHighApi = null;
} else {
if (mUploadCallbackForLowApi == null) {
return;
}
Uri result = data == null ? null : data.getData();
mUploadCallbackForLowApi.onReceiveValue(result);
mUploadCallbackForLowApi = null;
}
}

private void configWebView(WebView webView) {
WebSettings settings = webView.getSettings();
settings.setCacheMode(WebSettings.LOAD_NO_CACHE);
settings.setAllowFileAccess(true);
settings.setDomStorageEnabled(true);
settings.setJavaScriptEnabled(true);
webView.setWebViewClient(myWebViewClient);
webView.setWebChromeClient(myWebChromeClient);
}

private void openFilerChooser(ValueCallback<Uri> uploadMsg) {
mUploadCallbackForLowApi = uploadMsg;
startActivityForResult(Intent.createChooser(getFilerChooserIntent(), "File Chooser"), REQUEST_CODE_FILE_CHOOSER);
}

private Intent getFilerChooserIntent(http://www.my516.com) {
Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
intent.addCategory(Intent.CATEGORY_OPENABLE);
return intent;
}
}