由于某些原因，这个线程中的所有答案，在onActivityResult()中尝试对接收到的Uri进行后处理，比如获得图像的真实路径，然后使用BitmapFactory.decodeFile(path)来获得位图。

此步骤无需执行。ImageView类有一个叫做setImageURI(uri)的方法。将您的uri传递给它，您就应该完成了。

Uri imageUri = data.getData();
imageView.setImageURI(imageUri);

完整的工作示例可以在这里查看:http://androidbitmaps.blogspot.com/2015/04/loading-images-in-android-part-iii-pick.html

PS: 在要加载的图像太大而无法装入内存的情况下，在一个单独的变量中获取位图是有意义的，并且需要一个缩小操作来防止OurOfMemoryError，就像@siamii答案中所示的那样。

这是一个图像和视频的测试代码。它也适用于所有小于19和大于19的api。

图片:

if (Build.VERSION.SDK_INT <= 19) {
                        Intent i = new Intent();
                        i.setType("image/*");
                        i.setAction(Intent.ACTION_GET_CONTENT);
                        i.addCategory(Intent.CATEGORY_OPENABLE);
                        startActivityForResult(i, 10);
                    } else if (Build.VERSION.SDK_INT > 19) {
                        Intent intent = new Intent(Intent.ACTION_PICK, android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
                        startActivityForResult(intent, 10);
                    }

视频:

if (Build.VERSION.SDK_INT <= 19) {
                        Intent i = new Intent();
                        i.setType("video/*");
                        i.setAction(Intent.ACTION_GET_CONTENT);
                        i.addCategory(Intent.CATEGORY_OPENABLE);
                        startActivityForResult(i, 20);
                    } else if (Build.VERSION.SDK_INT > 19) {
                        Intent intent = new Intent(Intent.ACTION_PICK, android.provider.MediaStore.Video.Media.EXTERNAL_CONTENT_URI);
                        startActivityForResult(intent, 20);
                    }    

.

     @Override
    public void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (resultCode == Activity.RESULT_OK) {               
            if (requestCode == 10) {
                Uri selectedImageUri = data.getData();
                String selectedImagePath = getRealPathFromURI(selectedImageUri);
            } else if (requestCode == 20) {
                Uri selectedVideoUri = data.getData();
                String selectedVideoPath = getRealPathFromURI(selectedVideoUri);
            }
        }
     }

     public String getRealPathFromURI(Uri uri) {
            if (uri == null) {
                return null;
            }
            String[] projection = {MediaStore.Images.Media.DATA};
            Cursor cursor = getActivity().getContentResolver().query(uri, projection, null, null, null);
            if (cursor != null) {
                int column_index = cursor
                        .getColumnIndexOrThrow(MediaStore.Images.Media.DATA);
                cursor.moveToFirst();
                return cursor.getString(column_index);
            }
            return uri.getPath();
        }

你必须为一个结果开始画廊意图。

Intent i = new Intent(Intent.ACTION_PICK,
               android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
startActivityForResult(i, ACTIVITY_SELECT_IMAGE); 

然后在onActivityForResult中调用intent.getData()来获取图像的Uri。然后你需要从ContentProvider中获取图像。

这样做可以启动图库，并允许用户选择一张图片:

Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
intent.setType("image/*");
startActivityForResult(intent, IMAGE_PICK);

然后在onActivityResult()中使用返回的图像的URI来设置ImageView上的图像。

public class BrowsePictureActivity extends Activity {
private static final int SELECT_PICTURE = 1;

private String selectedImagePath;

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    ((Button) findViewById(R.id.Button01))
            .setOnClickListener(new OnClickListener() {

                public void onClick(View arg0) {

                    Intent intent = new Intent();
                    intent.setType("image/*");
                    intent.setAction(Intent.ACTION_GET_CONTENT);
                    startActivityForResult(Intent.createChooser(intent,
                            "Select Picture"), SELECT_PICTURE);
                }
            });
}

public void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (resultCode == RESULT_OK) {
        if (requestCode == SELECT_PICTURE) {
            Uri selectedImageUri = data.getData();
            selectedImagePath = getPath(selectedImageUri);
        }
    }
}

public String getPath(Uri uri) {

        if( uri == null ) {
            return null;
        }

        // this will only work for images selected from gallery
        String[] projection = { MediaStore.Images.Media.DATA };
        Cursor cursor = managedQuery(uri, projection, null, null, null);
        if( cursor != null ){
            int column_index = cursor
            .getColumnIndexOrThrow(MediaStore.Images.Media.DATA);
            cursor.moveToFirst();
            return cursor.getString(column_index);
        }

        return uri.getPath();
}

}

近5年后的最新答案:

原始答案中的代码不再可靠地工作，因为来自不同来源的图像有时会返回不同的内容URI，即content://而不是file://。一个更好的解决方案是简单地使用context.getContentResolver(). openinputstream (intent.getData())，因为它将返回一个你可以选择处理的InputStream。

例如，BitmapFactory.decodeStream()在这种情况下工作得很好，因为你也可以使用Options和inSampleSize字段来减少大图像的采样，避免内存问题。

但是，像谷歌Drive之类的东西会返回尚未实际下载的图像的uri。因此，您需要在后台线程上执行getContentResolver()代码。

最初的回答:

其他答案解释了如何发送意图，但没有很好地解释如何处理响应。下面是一些示例代码:

protected void onActivityResult(int requestCode, int resultCode, 
       Intent imageReturnedIntent) {
    super.onActivityResult(requestCode, resultCode, imageReturnedIntent); 

    switch(requestCode) { 
    case REQ_CODE_PICK_IMAGE:
        if(resultCode == RESULT_OK){  
            Uri selectedImage = imageReturnedIntent.getData();
            String[] filePathColumn = {MediaStore.Images.Media.DATA};

            Cursor cursor = getContentResolver().query(
                               selectedImage, filePathColumn, null, null, null);
            cursor.moveToFirst();

            int columnIndex = cursor.getColumnIndex(filePathColumn[0]);
            String filePath = cursor.getString(columnIndex);
            cursor.close();


            Bitmap yourSelectedImage = BitmapFactory.decodeFile(filePath);
        }
    }
}

在此之后，您已经将选中的图像存储在“yourSelectedImage”中，可以做任何您想做的事情。这段代码通过在ContentResolver数据库中获取图像的位置来工作，但这本身是不够的。每张图片大约有18列信息，从文件路径到“最后修改日期”，再到照片拍摄地点的GPS坐标，不过很多字段实际上并没有被使用。

To save time as you don't actually need the other fields, cursor search is done with a filter. The filter works by specifying the name of the column you want, MediaStore.Images.Media.DATA, which is the path, and then giving that string[] to the cursor query. The cursor query returns with the path, but you don't know which column it's in until you use the columnIndex code. That simply gets the number of the column based on its name, the same one used in the filtering process. Once you've got that, you're finally able to decode the image into a bitmap with the last line of code I gave.