将从相机拍摄的图像设置为 ImageView

Question

我正在尝试将从相机拍摄的图像设置为 ImageView。我启动相机意图，然后在 OnActivityResult 中收到 NullPointerException，我不明白该错误。

在这里，我启动相机意图并将图像存储在手机的图库中：

ContentValues values = new ContentValues();
values.put(MediaStore.Images.Media.TITLE, "New Picture");
imageUri = context.getContentResolver().insert(MediaStore.Images.Media.EXTERNAL_CONTENT_URI, values);
intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
pictureActionIntent.putExtra(MediaStore.EXTRA_OUTPUT, imageUri);
startActivityForResult(intent, CAMERA_REQUEST);

现在，相机的图像令牌保存在手机的图库中（高质量）。 在 onActivityResult 中，我想将图像放入 ImageView。这是我的代码：

else if (requestCode == CAMERA_REQUEST)
{
  if (resultCode == RESULT_OK)
   {
     imageUri = data.getData();
             try 
             {
               Bitmap bitmap = Media.getBitmap(getContentResolver(), imageUri); //NullPointerException
               myImageView.setImageBitmap(bitmap);
             } 
          catch (IOException e) 
             {
              e.printStackTrace();
             }

我有一个 NullPointerException，为什么？请问怎么解决？

Answer 1

这会将您的结果保存在 mediaStore 中，因此 data.getData(); 将返回 NULL：

pictureActionIntent.putExtra(MediaStore.EXTRA_OUTPUT, imageUri);

删除它，您将获得在 ImageView 上显示的数据。但是，如果您直接从data 获取图像，则图像质量很差

Answer 2

您的代码不完整，您还没有添加 logcat 错误！ 所以在这种情况下很难指导你！但是你想要达到的并不是那么难。试试这个：

public class LaunchCamera extends Activity {
 ImageView imVCature_pic;
 Button btnCapture;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_launch_camera);
  initializeControls();
 }

 private void initializeControls() {
  imVCature_pic=(ImageView)findViewById(R.id.imVCature_pic);
  btnCapture=(Button)findViewById(R.id.btnCapture);
  btnCapture.setOnClickListener(new OnClickListener() {

   @Override
   public void onClick(View v) {
    /* create an instance of intent
     * pass action android.media.action.IMAGE_CAPTURE 
     * as argument to launch camera
     */
    Intent intent = new Intent("android.media.action.IMAGE_CAPTURE");
    /*create instance of File with name img.jpg*/
    File file = new File(Environment.getExternalStorageDirectory()+File.separator + "img.jpg");
    /*put uri as extra in intent object*/
    intent.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(file));
    /*start activity for result pass intent as argument and request code */
    startActivityForResult(intent, 1);
   }
  });

 }

 @Override
 protected void onActivityResult(int requestCode, int resultCode, Intent data) {
  super.onActivityResult(requestCode, resultCode, data);
  //if request code is same we pass as argument in startActivityForResult
  if(requestCode==1){
   //create instance of File with same name we created before to get image from storage
   File file = new File(Environment.getExternalStorageDirectory()+File.separator + "img.jpg");
   //get bitmap from path with size of
   imVCature_pic.setImageBitmap(decodeSampledBitmapFromFile(file.getAbsolutePath(), 600, 450));
   }
 }
 public static Bitmap decodeSampledBitmapFromFile(String path,
   int reqWidth, int reqHeight) { 
  // First decode with inJustDecodeBounds=true to check dimensions
  final BitmapFactory.Options options = new BitmapFactory.Options();
  //Query bitmap without allocating memory
  options.inJustDecodeBounds = true;
  //decode file from path
  BitmapFactory.decodeFile(path, options);
  // Calculate inSampleSize
  // Raw height and width of image
  final int height = options.outHeight;
  final int width = options.outWidth;
  //decode according to configuration or according best match
  options.inPreferredConfig = Bitmap.Config.RGB_565;
  int inSampleSize = 1;
  if (height > reqHeight) {
   inSampleSize = Math.round((float)height / (float)reqHeight);
  }
  int expectedWidth = width / inSampleSize;
  if (expectedWidth > reqWidth) {
   //if(Math.round((float)width / (float)reqWidth) > inSampleSize) // If bigger SampSize..
   inSampleSize = Math.round((float)width / (float)reqWidth);
  }
  //if value is greater than 1,sub sample the original image
  options.inSampleSize = inSampleSize;
  // Decode bitmap with inSampleSize set
  options.inJustDecodeBounds = false;
  return BitmapFactory.decodeFile(path, options);
 }
}

完整的代码sn-p描述得很好here。