在 Android Eclipse 中旋转图像时出错

Posted 2023-04-18

【中文标题】在 Android Eclipse 中旋转图像时出错

【英文标题】：Error while rotating an image in Android Eclipse

【发布时间】：2013-01-11 19:42:16

【问题描述】：

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));
  

这是另一个类..

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;

// 私有静态最终浮点数 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);
    

它给出空指针异常错误..请帮助我，出了什么问题？

【参考方案1】：

在调用 b（您的位图）之前，您的 CustomOnItemSelected 对象是在 addListenerOnSpinnerItemSelection() 中创建的，它是从 onCreate 调用的。因此，当分配给 myBitmap 时，b 为空。

将您的 addListenerOnSpinnerItemSelection() 调用移至 onActivityResult() 以确保在调用 CustomOnItemSelected 构造函数之前创建您的位图。

【讨论】：

不，但我想做的是，首先加载图像。然后，如果要执行任何活动，则只需单击任何操作，例如“旋转”或“缩放”。

最初，我为“旋转”使用了不同的 xml 文件，然后它工作正常......