Question

这是我的主要代码..

public class MainActivity extends Activity {

private static int RESULT_LOAD_IMAGE = 1;
private Spinner spinner1;
Bitmap b;

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

     addListenerOnSpinnerItemSelection();

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


}

/*@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.activity_main, menu);
    return true;
}*/


@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);

    ImageView imageView = (ImageView) findViewById(R.id.imgView);

    if (requestCode == RESULT_LOAD_IMAGE && resultCode == RESULT_OK && null != data) {
        Uri selectedImage = data.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 picturePath = cursor.getString(columnIndex);
        cursor.close();

        b = BitmapFactory.decodeFile(picturePath);

        imageView.setImageBitmap(b);

    }


}

public void addListenerOnSpinnerItemSelection() {
    ImageView imageView = (ImageView) findViewById(R.id.imgView);
    spinner1 = (Spinner) findViewById(R.id.spinner1);
    spinner1.setOnItemSelectedListener(new CustomOnItemSelected(imageView, this , b));
  }

}

这是另一个班..

public class CustomOnItemSelected implements OnItemSelectedListener {

ImageView i;
Context c;
private Bitmap myBitmap;

CustomOnItemSelected(ImageView i,Context c, Bitmap b)
{
    this.i = i;
    this.c = c;
    myBitmap = b;
}

//private static final float ROTATE_FROM = 0.0f;

// private static final float ROTATE_TO = -10.0f * 360.0f;

public void onItemSelected（AdapterView parent，View view，int pos，long id）{ Toast.makeText（parent.getContext（） “OnItemSelectedListener：”+ parent.getItemAtPosition（pos）.toString（）， Toast.LENGTH_SHORT）.show（）;

   if(parent.getItemAtPosition(pos).toString().equals("Rotate"))
  {

       Matrix mat = new Matrix();
        mat.postRotate(90);
        Bitmap bMapRotate = Bitmap.createBitmap(myBitmap, 0, 0, myBitmap.getWidth(), myBitmap.getHeight(), mat, true); //GIVING ERROR ON THIS LINE...
        i.setImageBitmap(bMapRotate);
    }

它给出了空指针异常错误..请帮帮我，出了什么问题？

Answer 1

您的CustomOnItemSelected-object是在addListenerOnSpinnerItemSelection（）中创建的，在调用b（您的位图）之前从onCreate调用。因此，当分配给myBitmap时，b为null。

移动你的addListenerOnSpinnerItemSelection（） - 调用onActivityResult（）以确保在调用CustomOnItemSelected-constructor之前创建你的位图。

在Android Eclipse中旋转图像时出错

1 个答案: