android - 如何保存在 webview 中显示的图像？

Question

我想将 webview 中显示的图像保存到本地存储中，webview 应该已经缓存了它显示的图像，我如何访问缓存的图像并将它们保存到存储中？

Answer 1

然后你必须为你的 WebView设置一个WebViewClient并覆盖shouldOverrideUrlLoading和onLoadResource方法。让我给你一个简单的例子：

WebView yourWebView; // initialize it as always...
// this is the funny part:
yourWebView.setWebViewClient(yourWebClient);

// somewhere on your code...
WebViewClient yourWebClient = new WebViewClient(){
    // you tell the webclient you want to catch when a url is about to load
    @Override
    public boolean shouldOverrideUrlLoading(WebView  view, String  url){
        return true;
    }
    // here you execute an action when the URL you want is about to load
    @Override
    public void onLoadResource(WebView  view, String  url){
        if( url.equals("http://cnn.com") ){
            // do whatever you want
           //download the image from url and save it whereever you want
        }
    }
}

Answer 2

WebView webView = new WebView(this);
//your image is in webview

Picture picture = webView.capturePicture();
Canvas canvas = new Canvas();
picture.draw(canvas);
Bitmap image = Bitmap.createBitmap(picture.getWidth(),
picture.getHeight(),Config.ARGB_8888);
canvas.drawBitmap(mimage, 0, 0, null);
if(image != null) {
    ByteArrayOutputStream mByteArrayOS = new
    ByteArrayOutputStream();
    image.compress(Bitmap.CompressFormat.JPEG, 90, mByteArrayOS);
    try {
        fos = openFileOutput("image.jpg", MODE_WORLD_WRITEABLE);
        fos.write(mByteArrayOS.toByteArray());
        fos.close();
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

尝试以上从 webView 捕获图像

Answer 3

我确实使用了上面的代码并且它“工作”，但它只产生黑色图像，所以几个小时后这里是我的更正，现在它写在外部 SD 卡上，没有弃用风险或路径问题......

public void captureWV() {
    Picture picture = webview.capturePicture();
    Bitmap image = Bitmap.createBitmap(picture.getWidth(),picture.getHeight(), Config.ARGB_8888);
    Canvas canvas = new Canvas(image);
    picture.draw(canvas);
    if (image != null) {
        ByteArrayOutputStream mByteArrayOS = new ByteArrayOutputStream();
        image.compress(Bitmap.CompressFormat.JPEG, 90, mByteArrayOS);
        try {
            File sdCard = Environment.getExternalStorageDirectory();
            File dir = new File(sdCard.getAbsolutePath());
            File file = new File(dir, "filename.jpg");
            FileOutputStream fos = new FileOutputStream(file);
            fos.write(mByteArrayOS.toByteArray());
            fos.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

这也是我的 MainActivity 的开始

public class MainActivity extends Activity {
private static final String URL = "http://punto.gt"; //your website
WebView webview;
// your code here
}

Answer 4

也许您应该检查该文件是否存在于缓存文件中。

1. 获取 url 的哈希键。

   MessageDigest md;
   try {
       md = MessageDigest.getInstance(“SHA-1”);
   } catch (NoSuchAlgorithmException e) {
       return "";
   }
   md.update(url.getBytes());
   byte b[] = md.digest();
   

   Chromium 使用前 8 个字节的哈希码。所以也许你应该做

   int i;
   StringBuffer buf = new StringBuffer("");
   for (int offset = 0; offset < 8; ++offset) {
       i = b[8 - offset - 1];
       if (i < 0)
           i += 256;
       if (i < 16)
           buf.append("0");
       buf.append(Integer.toHexString(i));
   }
   

   然后你得到哈希字符串。chromium 中的缓存文件名是 hash + "_" + fileindex，通常文件名为零。所以文件名应该是hash_0；

2 从缓存文件中获取内容。

try {
    input = new FileInputStream(filename);
    FileOutputStream output = new FileOutputStream("/sdcard/img.jpg"); // save to this file
    input.skip(12); // length of key
    int len = input.read() + 12; 
    input.skip(len - 1); // skip the  key and the header
    int read;
    // magic  0xd8410d97456ffaf4;
    int flag = 0;
    while ((read = input.read()) != -1) {
          if ((flag == 0 && read == 0xd8) ||
          (flag == 1 && read == 0x41) ||
          (flag == 2 && read == 0x0d) ||
          (flag == 3 && read == 0x97) ||
          (flag == 4 && read == 0x45) ||
          (flag == 5 && read == 0x6f) ||
          (flag == 6 && read == 0xfa) ||
          (flag == 7 && read == 0xf4)) {
          flag++;
          if(flag == 8) {
              // success
              break;
          }
      } else if (flag > 0) {
          flag = 0;
      }
      output.write(read);
    }
    input.close();
    output.close();
    } catch (Exception e) {
    }
    return true;
} catch (Exception e) {
    return false;
}