Question

我正在显示SD卡中的图片。我在谷歌搜索了很多，并得到以下代码

我有一个按钮，点击即可调用相机功能。

public void onClick(View arg0) {


                // create intent with ACTION_IMAGE_CAPTURE action

         Intent intent = new Intent("android.media.action.IMAGE_CAPTURE");
            File photo = new File(Environment.getExternalStorageDirectory(),  "Pic.jpg");
            photoPath = Uri.fromFile(photo);

        intent.putExtra(MediaStore.EXTRA_OUTPUT,Uri.fromFile(photo));

            System.out.println(photoPath);
            startActivityForResult(intent, TAKE_PICTURE);
    }

我在onActivityResult函数中使用了以下代码。

protected void onActivityResult(int requestCode, int resultCode,
        Intent intent) {

     super.onActivityResult(requestCode, resultCode, intent);

     if (requestCode == TAKE_PICTURE && resultCode == RESULT_OK) {

                System.out.println("after activity"+photoPath);
                Uri selectedImage = photoPath;
                getContentResolver().notifyChange(selectedImage, null);
                ivThumbnailPhoto = (ImageView) findViewById(R.id.ivThumbnailPhoto);
                ContentResolver cr = getContentResolver();
                Bitmap bitmap;
                try {
                     bitmap = android.provider.MediaStore.Images.Media
                     .getBitmap(cr, selectedImage);

                     ivThumbnailPhoto.setImageBitmap(bitmap);
                    Toast.makeText(this, selectedImage.toString(),
                            Toast.LENGTH_LONG).show();
                } catch (Exception e) {
                    Toast.makeText(this, "Failed to load", Toast.LENGTH_SHORT)
                            .show();
                    Log.e("Camera", e.toString());
                }

            }

}

问题是我将photoPath值变为null并且最终会出现nullpointer异常。请帮我找出问题。

提前致谢

Answer 1

您将文件路径的值作为intent extra传递，这是正确的行为。

intent.putExtra(MediaStore.EXTRA_OUTPUT,Uri.fromFile(photo));//here  save this uri you are passing as extra.

在onActivityResult中，如果RESULT_CODE OK使用您URI以上传递的EXTRA_OUTPUT，则您将从相机获取null意图/数据，所以不要使用它。

编辑： - 当您退出活动并返回时，您的PhotoPath变量可能会变为NULL，这里有两个解决方案。

1）使photopath / uri静止。

2）使用以下代码在外出时保存，并在进入活动时获取值。

/**
 * Here we store the file url as it will be null after returning from camera
 * app
 */
@Override
protected void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    // save file url in bundle as it will be null on scren orientation
    // changes
    outState.putParcelable("file_uri", photopath);
}

/*
 * Here we restore the fileUri again
 */
@Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
    super.onRestoreInstanceState(savedInstanceState);

    // get the path
    photoPath = savedInstanceState.getParcelable("file_uri");
}

android中的图像显示

1 个答案: