Hey there! Let's figure out why your WebView's image upload button isn't working—this is a super common issue, and we can fix it by checking a few key areas. Let's break it down step by step:

First, double-check your AndroidManifest.xml for the permissions needed to access device storage and internet (though you said the app runs fine overall, internet permission is probably already there, but storage is critical for uploads):

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

Important note: For Android 6.0 (API level 23) and above, you can't just declare these in the manifest—you need to ask the user for storage permissions dynamically in your code. If you skip this step, the app won't be able to access photos/files even if the permissions are listed.

WebView doesn't handle file uploads out of the box—you need to enable JavaScript and set up a WebChromeClient to manage the file selection prompt:

• First, turn on JavaScript in your WebView settings:

webView.getSettings().setJavaScriptEnabled(true);
webView.getSettings().setJavaScriptCanOpenWindowsAutomatically(true);

• Next, set a WebChromeClient and override the onShowFileChooser method (this is the core part that triggers the system file picker):

// Declare this as a class variable to hold the callback
private ValueCallback<Uri[]> mFilePathCallback;
private static final int FILE_CHOOSER_REQUEST_CODE = 1001;

// Then set the WebChromeClient
webView.setWebChromeClient(new WebChromeClient() {
    @Override
    public boolean onShowFileChooser(WebView webView, ValueCallback<Uri[]> filePathCallback, FileChooserParams fileChooserParams) {
        // Save the callback so we can send the result back later
        if (mFilePathCallback != null) {
            mFilePathCallback.onReceiveValue(null);
        }
        mFilePathCallback = filePathCallback;

        // Open the system file picker
        Intent intent = fileChooserParams.createIntent();
        try {
            startActivityForResult(intent, FILE_CHOOSER_REQUEST_CODE);
        } catch (ActivityNotFoundException e) {
            mFilePathCallback = null;
            Toast.makeText(YourActivity.this, "File picker not available", Toast.LENGTH_SHORT).show();
            return false;
        }
        return true;
    }
});

• Don't forget to handle the result from the file picker in onActivityResult:

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    
    if (requestCode == FILE_CHOOSER_REQUEST_CODE) {
        if (mFilePathCallback == null) return;
        
        Uri[] results = null;
        if (resultCode == RESULT_OK && data != null) {
            // Get the selected file's URI
            String dataString = data.getDataString();
            if (dataString != null) {
                results = new Uri[]{Uri.parse(dataString)};
            }
        }
        
        // Send the result back to the WebView
        mFilePathCallback.onReceiveValue(results);
        mFilePathCallback = null;
    }
}

If your app targets Android 10 (API 29) or higher, Google's Scoped Storage might block access to files. Add this attribute to your <application> tag in AndroidManifest.xml to temporarily bypass it (or adjust your code to use Scoped Storage properly):

<application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:requestLegacyExternalStorage="true" <!-- Add this line -->
    android:roundIcon="@mipmap/ic_launcher_round"
    android:supportsRtl="true"
    android:theme="@style/AppTheme">
    ...
</application>

Before diving deeper into Android code, test the upload button in the regular Chrome browser on your phone. If it doesn't work there either, the problem is with the web page's JavaScript or HTML, not your WebView setup.

If you can share your actual AndroidManifest.xml code and any existing WebView setup you have, I can help you spot exactly what's missing. 😊

内容的提问来源于stack exchange，提问作者Dhruv Patel