Question

我正在制作应用程序进行练习。在应用程序中，用户可以拍摄照片，照片将保留在外部存储器中。在下面有一些我的应用程序的代码。

  public class MainActivity extends AppCompatActivity implements ActionBar.TabListener {
public static final String TAG = MainActivity.class.getSimpleName();
public static final int TAKE_PHOTO_REQUEST = 0;
public static final int TAKE_VIDEO_REQUEST = 1;
public static final int PICK_PHOTO_REQUEST = 2;
public static final int PICK_VIDEO_REQUEST = 3;
public static final int MEDIA_TYPE_IMAGE = 4;
public static final int MEDIA_TYPE_VIDEO = 5;

private Uri mMediaUri;

private DialogInterface.OnClickListener mDialogListener = new DialogInterface.OnClickListener() {
    @Override
    public void onClick(DialogInterface dialog, int which) {
        switch (which){
            case 0:
                Intent takePhotoIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
                mMediaUri = getOutPutMediaFileUri(MEDIA_TYPE_IMAGE);
                if (mMediaUri == null) {
                    //display an error
                    Toast.makeText(MainActivity.this, R.string.error_external_storage, Toast.LENGTH_LONG).show();
                } else {
                    takePhotoIntent.putExtra(MediaStore.EXTRA_OUTPUT, mMediaUri);
                    startActivityForResult(takePhotoIntent, TAKE_PHOTO_REQUEST);
                }
                break;


            case 1:
                Intent videoIntent = new Intent(MediaStore.ACTION_VIDEO_CAPTURE);
                mMediaUri = getOutPutMediaFileUri(MEDIA_TYPE_VIDEO);
                if (mMediaUri == null) {
                    //display an error
                    Toast.makeText(MainActivity.this, R.string.error_external_storage, Toast.LENGTH_LONG).show();
                } else {
                    videoIntent.putExtra(MediaStore.EXTRA_OUTPUT, mMediaUri);
                    videoIntent.putExtra(MediaStore.EXTRA_DURATION_LIMIT, 10);
                    videoIntent.putExtra(MediaStore.EXTRA_VIDEO_QUALITY, 0); //0 for low quality
                    startActivityForResult(videoIntent, TAKE_VIDEO_REQUEST);
                }
                break;


            case 2:
                break;
            case 3:
                break;
        }
    }





    private Uri getOutPutMediaFileUri(int mediaType) {
                    if (isExternalStorageAvailable()) {
        //Get the external storage directory
            String appName = MainActivity.this.getString(R.string.app_name);
            File mediaStorageDir = new File(
                             Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES), appName);
        //Create our subdirectory
            if (! mediaStorageDir.exists()){
                if (! mediaStorageDir.mkdirs()){
                    Log.d(TAG, "failed to create directory");
                    return null;
                }
            }
               //Create file name
               //Create the file
                        File mediaFile;
                        Date now = new Date();
                        String timestamp = new SimpleDateFormat("yyyyMMdd_HHmmss", Locale.US).format(now);
                        String path = mediaStorageDir.getPath() + File.separator;
                        if (mediaType == MEDIA_TYPE_IMAGE) {
                        mediaFile = new File(path + "IMG_" + timestamp + ".jpg");
                        } else if (mediaType == MEDIA_TYPE_VIDEO) {
                        mediaFile = new File(path + "VID_" + timestamp + ".mp4");
                        } else {
                        return null;
                        }
                        Log.d(TAG, "File: " + Uri.fromFile(mediaFile));
                        //Return the file's uri
                        return Uri.fromFile(mediaFile);
                        } else {
                        return null;
                        }
                        }

                        private boolean isExternalStorageAvailable() {
                        String state = Environment.getExternalStorageState();
                        if (state.equals(Environment.MEDIA_MOUNTED)) {
                        return true;
                        } else {
                        return false;
                        }
                        }
};

我在清单文件中添加了这两行

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-feature android:name="android.hardware.camera2" android:required="true"/>

但是当我运行应用程序并选择拍摄照片时，会出现一个吐司，并说访问外部存储器时出现问题。并且在日志中表示无法创建目录。[注意：吐司是仅在mMediaUri为空时才显示]

我还在我的模拟器中定义了sdcard

为什么mMediaUri返回null; 那么，我的代码出了什么问题。我的代码中没有看到任何错误。请解决这个问题。

访问Android模拟器外部存储时出错

0 个答案: