Android; BitmapFactory.decodeFile(文件) returns 空，已知文件存在

Question

我正在尝试渲染我用以下 class 拍摄的照片，其中 returns 使用的文件：

public File takePhoto(){
    Intent pictureIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
    File destination= null;
    try {
        destination = createFile();
    } catch (IOException error) {
        Log.v(TAG, "IO error, reading exception");
        String errorMessage = error.getMessage();
        Log.v(TAG, errorMessage);
        String errorCauseMessage = error.getCause().getMessage();
       Log.v(TAG, errorCauseMessage);
    }
    if (destination != null){
        Log.v(TAG, "destination was written");
        pictureIntent.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(destination));
        parentActivity.startActivityForResult(pictureIntent, REQUEST_TAKE_PHOTO);
        Log.v(TAG, "destination was: " + destination.getAbsolutePath());
    }
    else {
        Log.v(TAG, "destination was not written");
    }``
    return destination;

然后在以下代码中使用结果：

Log.v(TAG, "adding picture");
            PhotoHandler photoHandler = new PhotoHandler(getPackageManager(), PolishCreateActivity.this);
            File imgFile = photoHandler.takePhoto();
            if (imgFile == null) {
                Toast.makeText(this, ERROR_TOAST_TEXT, Toast.LENGTH_SHORT).show();
            } else {
                Log.v(TAG, "Picture added");

                Log.v(TAG, "storing directory");
                img = imgFile.getAbsolutePath();
                Log.v(TAG, "Directory stored");

                Log.v(TAG, "Displaying picture");
                LinearLayout layout = (LinearLayout) findViewById(R.id.rootLayout);
                if (imageViewExists == Boolean.TRUE) {
                    ImageView oldView = (ImageView) findViewById(R.id.imageViewID);
                    layout.removeView(oldView);
                }
                UIHelper uiHelper = new UIHelper(this.getApplicationContext());
                ImageView imageView = uiHelper.getImageViewFromPath(imgFile);
                imageView.setId(R.id.imageViewID);
                layout.addView(imageView);
                imageViewExists = Boolean.TRUE;
                Log.v(TAG, "picture displayed");

并传递给此方法，如 imgFile:

public ImageView getImageViewFromPath(File imgFile) {
    ImageView imageView = new ImageView(context);
    Bitmap imgBM = null;
    if (imgFile.exists()) {
        Log.v(TAG, "image file exists");
        imgBM = BitmapFactory.decodeFile(imgFile.getAbsolutePath());
        if (imgBM == null){
            Log.v(TAG, "Bitmap returned was null");
        }
    }
    imageView.setImageBitmap(imgBM);
    imageView.setLayoutParams(new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT));
    Log.v(TAG, "ImageView was created");
    return imageView;
}

问题是 BitmapFactory.decodeFile(imgFile.getAbsolutePath) returns 每次我运行它，即使文件存在（我可以告诉因为我得到"if (imgFile.exists())" 正文中的日志消息）。找了很久的解决方法，一直没有找到解决办法。我已经测试过它不会导致 outOfMemory 异常，事实并非如此。任何帮助将不胜感激。

Answer 1

检查 imgFile.getAbsolutePath() 的值。

这个值可能为空或非法。

使用调试模式或记录此值以记录 cat。

Answer 2

takePhoto 开始 activity 结果：

parentActivity.startActivityForResult(pictureIntent, REQUEST_TAKE_PHOTO);

但是您的代码会像这样立即完成，但事实并非如此。该文件当然会在那里，但它总是 0 字节大。

您需要覆盖 onActivityResult() 并从那里处理文件内容。

Answer 3

好的，我通过切换到通过 onActivityResult 从 Intent 获取位图解决了这个问题。

    @Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (requestCode == REQUEST_IMAGE_CAPTURE && resultCode == RESULT_OK){
        Bundle extras = data.getExtras();
        photo = (Bitmap) extras.get("data");
        LinearLayout layout = (LinearLayout) findViewById(R.id.rootLayout);
        layout.addView(UIHelper.getImageViewFromPath(photo, getApplicationContext()));
    }
}

不过我还需要保存位图。

Answer 4

检查您使用的 sdk 版本 sdk 版本 23 或更高版本您必须获得在设备上读写的权限..检查下面的代码可能会解决您的问题

@Override
public void onClick(View v) {
 if((ContextCompat.checkSelfPermission(MainActivity.this,                                  
            Manifest.permission.READ_EXTERNAL_STORAGE)!=PackageManager.PERMISSION_GRANTED)       
                || (ContextCompat.checkSelfPermission(MainActivity.this,
                Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED))

        {
            ActivityCompat.requestPermissions
                    (MainActivity.this, new String[]{
                            Manifest.permission.READ_EXTERNAL_STORAGE,
                            Manifest.permission.WRITE_EXTERNAL_STORAGE
                    },MY_PERMISSIONS_REQUEST_READ_AND_WRITE_EXTERNAL_STORAGE);
        }
}

Android; BitmapFactory.decodeFile(文件) returns 空，已知文件存在

Android; BitmapFactory.decodeFile(file) returns null, file is known to exists

java

android

bitmapfactory