javascript - 如何在android中发送base64字符串？

Question

我正在尝试制作Hydrid应用程序，其中HTML页面上有一个“按钮”。每当我单击该按钮时，我想调用android代码函数(工作正常)当我从 javascript 调用 test 函数时)。现在我想在单击按钮时捕获图像我从下面的网址寻求帮助。 Capture Image from Camera and Display in Activity我喜欢这个包 com.example.myapp.myapplication;

import android.Manifest;
import android.app.Activity;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.graphics.Bitmap;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.util.Base64;
import android.util.Log;
import android.webkit.JavascriptInterface;
import android.webkit.WebChromeClient;
import android.webkit.WebView;
import android.widget.Toast;

import java.io.ByteArrayOutputStream;

public class MainActivity extends AppCompatActivity {
    private static final int CAMERA_REQUEST = 1888;
    private static final int MY_CAMERA_PERMISSION_CODE = 100;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        WebView webView = (WebView) findViewById(R.id.webview);
        // webView.loadUrl("http://1.5.20.97:3671");
        webView.loadUrl("http://15.16.74.160:6019");
        JavaScriptInterface jsInterface = new JavaScriptInterface(this);
        webView.getSettings().setJavaScriptEnabled(true);
        webView.setWebChromeClient(new WebChromeClient());
        webView.addJavascriptInterface(jsInterface, "JSInterface");
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        if (requestCode == MY_CAMERA_PERMISSION_CODE) {
            if (grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                Toast.makeText(this, "camera permission granted", Toast.LENGTH_LONG).show();
                Intent cameraIntent = new Intent(android.provider.MediaStore.ACTION_IMAGE_CAPTURE);
                startActivityForResult(cameraIntent, CAMERA_REQUEST);
            } else {
                Toast.makeText(this, "camera permission denied", Toast.LENGTH_LONG).show();
            }
        }

    }

    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        if (requestCode == CAMERA_REQUEST && resultCode == Activity.RESULT_OK) {
            Bitmap photo = (Bitmap) data.getExtras().get("data");
          //  Log.d("My map",photo,"");
        }
    }

    public void checkTest(){
        if (checkSelfPermission(Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) {
            requestPermissions(new String[]{Manifest.permission.CAMERA}, MY_CAMERA_PERMISSION_CODE);
        } else {
            Intent cameraIntent = new Intent(android.provider.MediaStore.ACTION_IMAGE_CAPTURE);
            startActivityForResult(cameraIntent, CAMERA_REQUEST);
        }
    }
}


class JavaScriptInterface {
    private MainActivity activity;


    public JavaScriptInterface(MainActivity activity) {
        this.activity = activity;
    }

    @JavascriptInterface
    public void test() {
        this.activity.checkTest();
    }


    @JavascriptInterface
    public String bitMapToBase64()
    {
        ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
        //add support for jpg and more.
        bitMap.compress(Bitmap.CompressFormat.PNG, 50, byteArrayOutputStream);
        byte[] byteArray = byteArrayOutputStream .toByteArray();

        String encoded = Base64.encodeToString(byteArray, Base64.DEFAULT);

        return encoded;
    }


}

我遇到导入错误

我正在尝试调用一个打开相机并捕获图像并返回 JavaScript 的 android 函数。

在 javascript 上我正在调用这样的函数

console.log(window.JSInterface.test())

Answer 1

因此，要在从相机捕获图像时返回到 webView，请将 onActivityResult 方法更改为此

protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (requestCode == CAMERA_REQUEST && resultCode == Activity.RESULT_OK) {
        photo = (Bitmap) data.getExtras().get("data");
        if (webView != null)
           webView.loadUrl("http://125.16.74.160:30019");
    }
}

此外，您还应该将位图声明为全局静态变量，如下所示

公共(public)静态位图照片；

然后bitMapToBase64就变成这样了

@JavascriptInterface
public String bitMapToBase64()
{
  if (MainActivity.photo != null) {
    ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
    //add support for jpg and more.
    MainActivity.photo.compress(Bitmap.CompressFormat.PNG, 50, byteArrayOutputStream);
    byte[] byteArray = byteArrayOutputStream .toByteArray();

    String encoded = Base64.encodeToString(byteArray, Base64.DEFAULT);

    return encoded;
  }
  return "null image";
}

在 JavaScript 端，您检查 bitMapToBase64 函数的返回值是否不同于“空图像”，您将 Base64 图像转换为 Blob 或图像对象，然后将其显示在 div 中。

下面是如何将 Base64 字符串转换为图像对象并将其附加到正文的示例

var image = new Image();
image.src = 'data:image/png;base64,iVBORw0K...';
document.body.appendChild(image);