Android WebView那些坑之上传文件

时间 2019-12-08

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最近公司项目须要在WebView上调用手机系统相册来上传图片，开发过程当中发如今不少机器上没法正常唤起系统相册来选择图片。android

解决问题以前咱们先来讲说WebView上传文件的逻辑：当咱们在Web页面上点击选择文件的控件(<input type="file">)时，会回调WebChromeClient下的openFileChooser()（5.0及以上系统回调onShowFileChooser()）。这个时候咱们在openFileChooser方法中经过Intent打开系统相册或者支持该Intent的第三方应用来选择图片。like this：git

public void openFileChooser(ValueCallback<Uri> valueCallback, String acceptType, String capture) {
    uploadMessage = valueCallback;
       openImageChooserActivity();
}

private void openImageChooserActivity() {
    Intent i = new Intent(Intent.ACTION_GET_CONTENT);
    i.addCategory(Intent.CATEGORY_OPENABLE);
    i.setType("image/*");
    startActivityForResult(Intent.createChooser(i, 
                "Image Chooser"), FILE_CHOOSER_RESULT_CODE);
}

最后咱们在onActivityResult()中将选择的图片内容经过ValueCallback的onReceiveValue方法返回给WebView，而后经过js上传。代码以下：github

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    if (requestCode == FILE_CHOOSER_RESULT_CODE) {
        Uri result = data == null || resultCode != RESULT_OK ? null : data.getData();
        if (uploadMessage != null) {
            uploadMessage.onReceiveValue(result);
            uploadMessage = null;
        }
    }
}

PS:ValueCallbacks是WebView组件经过openFileChooser()或者onShowFileChooser()提供给咱们的，它里面包含了一个或者一组Uri,而后咱们在onActivityResult()里将Uri传给ValueCallbacks的onReceiveValue()方法，这样WebView就知道咱们选择了什么文件。web

到这里你可能要问了，说了这么多仍是没解释为何在不少机型上没法唤起系统相册或者第三方app来选择图片啊？！这是由于为了最求完美的Google攻城狮们对openFileChooser作了屡次修改，在5.0上更是将回调方法该为了onShowFileChooser。因此为了解决这一问题，兼容各个版本，咱们须要对openFileChooser()进行重载，同时针对5.0及以上系统提供onShowFileChooser()方法：app

webview.setWebChromeClient(new WebChromeClient() {

        // For Android < 3.0
        public void openFileChooser(ValueCallback<Uri> valueCallback) {
            ***
        }

        // For Android  >= 3.0
        public void openFileChooser(ValueCallback valueCallback, String acceptType) {
            ***
        }

        //For Android  >= 4.1
        public void openFileChooser(ValueCallback<Uri> valueCallback, 
                String acceptType, String capture) {
            ***
        }

        // For Android >= 5.0
        @Override
        public boolean onShowFileChooser(WebView webView, 
                ValueCallback<Uri[]> filePathCallback, 
                WebChromeClient.FileChooserParams fileChooserParams) {
            ***
            return true;
        }
    });

你们应该注意到onShowFileChooser()中的ValueCallback包含了一组Uri(Uri[]),因此针对5.0及以上系统，咱们还须要对onActivityResult()作一点点处理。这里不作描述，最后我再贴上完整代码。ide

当处理完这些后你觉得就万事大吉了？！当初我也这样天真，但当咱们打好release包测试的时候却又发现无法选择图片了！！！真是坑了个爹啊！！！无奈去翻WebChromeClient的源码，发现openFileChooser()是系统API，咱们的release包是开启了混淆的，因此在打包的时候混淆了openFileChooser()，这就致使没法回调openFileChooser()了。测试

/**
 * Tell the client to open a file chooser.
 * @param uploadFile A ValueCallback to set the URI of the file to upload.
 *      onReceiveValue must be called to wake up the thread.a
 * @param acceptType The value of the 'accept' attribute of the input tag
 *         associated with this file picker.
 * @param capture The value of the 'capture' attribute of the input tag
 *         associated with this file picker.
 *
 * @deprecated Use {@link #showFileChooser} instead.
 * @hide This method was not published in any SDK version.
 */
@SystemApi
@Deprecated
public void openFileChooser(ValueCallback<Uri> uploadFile, String acceptType, String capture) {
    uploadFile.onReceiveValue(null);
}

解决方案也很简单，直接不混淆openFileChooser()就行了。ui

-keepclassmembers class * extends android.webkit.WebChromeClient{
       public void openFileChooser(...);
}

支持关于上传文件的全部坑都填完了，最后附上完整源码：
(源码地址:https://github.com/BaronZ88/WebViewSample)this

public class MainActivity extends AppCompatActivity {

    private ValueCallback<Uri> uploadMessage;
    private ValueCallback<Uri[]> uploadMessageAboveL;
    private final static int FILE_CHOOSER_RESULT_CODE = 10000;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        WebView webview = (WebView) findViewById(R.id.web_view);
        assert webview != null;
        WebSettings settings = webview.getSettings();
        settings.setUseWideViewPort(true);
        settings.setLoadWithOverviewMode(true);
        settings.setJavaScriptEnabled(true);
        webview.setWebChromeClient(new WebChromeClient() {

            // For Android < 3.0
            public void openFileChooser(ValueCallback<Uri> valueCallback) {
                uploadMessage = valueCallback;
                openImageChooserActivity();
            }

            // For Android  >= 3.0
            public void openFileChooser(ValueCallback valueCallback, String acceptType) {
                uploadMessage = valueCallback;
                openImageChooserActivity();
            }

            //For Android  >= 4.1
            public void openFileChooser(ValueCallback<Uri> valueCallback, String acceptType, String capture) {
                uploadMessage = valueCallback;
                openImageChooserActivity();
            }

            // For Android >= 5.0
            @Override
            public boolean onShowFileChooser(WebView webView, ValueCallback<Uri[]> filePathCallback, WebChromeClient.FileChooserParams fileChooserParams) {
                uploadMessageAboveL = filePathCallback;
                openImageChooserActivity();
                return true;
            }
        });
        String targetUrl = "file:///android_asset/up.html";
        webview.loadUrl(targetUrl);
    }

    private void openImageChooserActivity() {
        Intent i = new Intent(Intent.ACTION_GET_CONTENT);
        i.addCategory(Intent.CATEGORY_OPENABLE);
        i.setType("image/*");
        startActivityForResult(Intent.createChooser(i, "Image Chooser"), FILE_CHOOSER_RESULT_CODE);
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (requestCode == FILE_CHOOSER_RESULT_CODE) {
            if (null == uploadMessage && null == uploadMessageAboveL) return;
            Uri result = data == null || resultCode != RESULT_OK ? null : data.getData();
            if (uploadMessageAboveL != null) {
                onActivityResultAboveL(requestCode, resultCode, data);
            } else if (uploadMessage != null) {
                uploadMessage.onReceiveValue(result);
                uploadMessage = null;
            }
        }
    }

    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
    private void onActivityResultAboveL(int requestCode, int resultCode, Intent intent) {
        if (requestCode != FILE_CHOOSER_RESULT_CODE || uploadMessageAboveL == null)
            return;
        Uri[] results = null;
        if (resultCode == Activity.RESULT_OK) {
            if (intent != null) {
                String dataString = intent.getDataString();
                ClipData clipData = intent.getClipData();
                if (clipData != null) {
                    results = new Uri[clipData.getItemCount()];
                    for (int i = 0; i < clipData.getItemCount(); i++) {
                        ClipData.Item item = clipData.getItemAt(i);
                        results[i] = item.getUri();
                    }
                }
                if (dataString != null)
                    results = new Uri[]{Uri.parse(dataString)};
            }
        }
        uploadMessageAboveL.onReceiveValue(results);
        uploadMessageAboveL = null;
    }
}

源码地址:https://github.com/BaronZ88/W...

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