android - 如何在从内部存储中选择的 imageView 上显示图像？

Question

我不熟悉在 android 中处理图像。我想从内部存储加载图像，但它给了我权限被拒绝的错误，然后我将权限添加到 android list 文件。但是我仍然无法完成我的任务。

这是我的代码:

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.ImageView;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ImageView image = (ImageView)findViewById(R.id.imageView);
        Bitmap bm = BitmapFactory.decodeFile("/storage/emulated/0/DCIM/Camera/IMG_20151102_193132.jpg");
        image.setImageBitmap(bm);

    }
}

日志:

01-16 15:16:11.345 6533-6533/com.example.jaytanna.imagemap E/BitmapFactory: Unable to decode stream: java.io.FileNotFoundException: /storage/emulated/0/DCIM/Camera/IMG_20151102_193132.jpg: open failed: EACCES (Permission denied)

它没有显示任何图像。请帮我解决这个问题。谢谢。

Answer 1

检查这个

     File imgFile = new  File("/storage/emulated/0/DCIM/Camera/IMG_20151102_193132.jpg");
      if(imgFile.exists()){

        Bitmap myBitmap = BitmapFactory.decodeFile(imgFile.getAbsolutePath());

        ImageView myImage = (ImageView) findViewById(R.id.imageviewTest);

        myImage.setImageBitmap(myBitmap);

      };

并将此权限包含在 list 文件中:

<manifest>
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    ...
    <application>
        ...
        <activity> 
            ...
        </activity>
    </application>
</manifest> 

对于 API 23+，您需要请求读/写权限，即使它们已经在您的 list 中。

// Storage Permissions
private static final int REQUEST_EXTERNAL_STORAGE = 1;
private static String[] PERMISSIONS_STORAGE = {
        Manifest.permission.READ_EXTERNAL_STORAGE,
        Manifest.permission.WRITE_EXTERNAL_STORAGE
};

/**
 * Checks if the app has permission to write to device storage
 *
 * If the app does not has permission then the user will be prompted to grant permissions
 *
 * @param activity
 */
public static void verifyStoragePermissions(Activity activity) {
    // Check if we have write permission
    int permission = ActivityCompat.checkSelfPermission(activity, Manifest.permission.WRITE_EXTERNAL_STORAGE);

    if (permission != PackageManager.PERMISSION_GRANTED) {
        // We don't have permission so prompt the user
        ActivityCompat.requestPermissions(
                activity,
                PERMISSIONS_STORAGE,
                REQUEST_EXTERNAL_STORAGE
        );
    }
}

并处理响应，一些例子:

@Override
public void onRequestPermissionsResult(int requestCode,
        String permissions[], int[] grantResults) {
    switch (requestCode) {
        case MY_PERMISSIONS_REQUEST_READ_CONTACTS: {
            // If request is cancelled, the result arrays are empty.
            if (grantResults.length > 0
                && grantResults[0] == PackageManager.PERMISSION_GRANTED) {

                // permission was granted, yay! Do the
                // contacts-related task you need to do.

            } else {

                // permission denied, boo! Disable the
                // functionality that depends on this permission.
            }
            return;
        }

        // other 'case' lines to check for other
        // permissions this app might request
    }
}

有关请求 API 23+ 权限的官方文档，请查看 https://developer.android.com/training/permissions/requesting.html