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Android WebView那些坑之上傳文件示例

更新時間：2017年01月24日 14:28:43 作者：BaronZhang

本篇文章主要介紹了Android WebView那些坑之上傳文件示例，具有一定的參考價值，有興趣的可以了解一下。

最近公司項目需要在WebView上調(diào)用手機系統(tǒng)相冊來上傳圖片，開發(fā)過程中發(fā)現(xiàn)在很多機器上無法正常喚起系統(tǒng)相冊來選擇圖片。

解決問題之前我們先來說說WebView上傳文件的邏輯：當(dāng)我們在Web頁面上點擊選擇文件的控件(<input type="file">)時，會回調(diào)WebChromeClient下的openFileChooser()（5.0及以上系統(tǒng)回調(diào)onShowFileChooser()）。這個時候我們在openFileChooser方法中通過Intent打開系統(tǒng)相冊或者支持該Intent的第三方應(yīng)用來選擇圖片。like this：

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);
}

最后我們在onActivityResult()中將選擇的圖片內(nèi)容通過ValueCallback的onReceiveValue方法返回給WebView，然后通過js上傳。代碼如下：

@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組件通過openFileChooser()或者onShowFileChooser()提供給我們的，它里面包含了一個或者一組Uri,然后我們在onActivityResult()里將Uri傳給ValueCallbacks的onReceiveValue()方法，這樣WebView就知道我們選擇了什么文件。

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;
  }
 });

到這里你可能要問了，說了這么多還是沒解釋為什么在很多機型上無法喚起系統(tǒng)相冊或者第三方app來選擇圖片??？！這是因為為了最求完美的Google攻城獅們對openFileChooser做了多次修改，在5.0上更是將回調(diào)方法該為了onShowFileChooser。所以為了解決這一問題，兼容各個版本，我們需要對openFileChooser()進行重載，同時針對5.0及以上系統(tǒng)提供onShowFileChooser()方法：

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;
  }
 });

大家應(yīng)該注意到onShowFileChooser()中的ValueCallback包含了一組Uri(Uri[]),所以針對5.0及以上系統(tǒng)，我們還需要對onActivityResult()做一點點處理。這里不做描述，最后我再貼上完整代碼。

當(dāng)處理完這些后你以為就萬事大吉了？！當(dāng)初我也這樣天真，但當(dāng)我們打好release包測試的時候卻又發(fā)現(xiàn)沒法選擇圖片了?。?！真是坑了個爹啊?。?！無奈去翻WebChromeClient的源碼，發(fā)現(xiàn)openFileChooser()是系統(tǒng)API，我們的release包是開啟了混淆的，所以在打包的時候混淆了openFileChooser()，這就導(dǎo)致無法回調(diào)openFileChooser()了。

/**
 * 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);
}

解決方案也很簡單，直接不混淆openFileChooser()就好了。

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

支持關(guān)于上傳文件的所有坑都填完了，最后附上完整源碼：

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;
 }
}

源碼地址: http://xiazai.jb51.net/201701/yuanma/WebViewSample_jb51.rar

以上就是本文的全部內(nèi)容，希望對大家的學(xué)習(xí)有所幫助，也希望大家多多支持腳本之家。

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