动态加载jpg到Canvas

Question

我正在尝试将已保存文件中的jpg加载到画布中，以便能够通过触摸和拖动来移动jpg。我可以在活动中获取图像路径，如何将其加载到画布中并使其可移动？）

这是我的主要活动：

public class MainActivity extends Activity {
private static final int GALLERY_INTENT = 0;
   @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        Intent galleryIntent = new Intent(
                Intent.ACTION_PICK,
                android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
        startActivityForResult(galleryIntent, 0);


        setContentView(R.layout.activity_main);



    }

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



    if (requestCode == GALLERY_INTENT) {
        if (resultCode == Activity.RESULT_OK) {
            Uri selectedImage = data.getData();
            String[] filePathColumn = { MediaColumns.DATA };

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

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

            File imgFile = new File(picturePath);
        }
    }
}

和我的类（在activity_main.xml中添加）。我目前只是画一个图标作为POC。但是我需要从主要活动中的意图结果中加载一个jpg。

public class TouchViewClass extends View {
private Drawable mIcon;

private float mPosX;
private float mPosY;
private Bitmap mSourceImage;
private float mLastTouchX;
private float mLastTouchY;

private static final int INVALID_POINTER_ID = -1;

 // The ‘active pointer’ is the one currently moving our object.
 private int mActivePointerId = INVALID_POINTER_ID;

public TouchViewClass(Context context) {
    this(context, null, 0);
}

public TouchViewClass(Context context, AttributeSet attrs) {
    this(context, attrs, 0);
}

public TouchViewClass(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
    mIcon = context.getResources().getDrawable(R.drawable.ic_launcher);
    mIcon.setBounds(0, 0, mIcon.getIntrinsicWidth(), mIcon.getIntrinsicHeight());
}

@Override
public void onDraw(Canvas canvas) {
    super.onDraw(canvas);

    canvas.save();
    canvas.translate(mPosX, mPosY);
    mIcon.draw(canvas);
    canvas.restore();
}

@Override
public boolean onTouchEvent(MotionEvent ev) {
    final int action = ev.getAction();
    switch (action & MotionEvent.ACTION_MASK) {
    case MotionEvent.ACTION_DOWN: {
        final float x = ev.getX();
        final float y = ev.getY();

        mLastTouchX = x;
        mLastTouchY = y;

        // Save the ID of this pointer
        mActivePointerId = ev.getPointerId(0);
        break;
    }

    case MotionEvent.ACTION_MOVE: {
        // Find the index of the active pointer and fetch its position
        final int pointerIndex = ev.findPointerIndex(mActivePointerId);
        final float x = ev.getX(pointerIndex);
        final float y = ev.getY(pointerIndex);

        final float dx = x - mLastTouchX;
        final float dy = y - mLastTouchY;

        mPosX += dx;
        mPosY += dy;

        mLastTouchX = x;
        mLastTouchY = y;

        invalidate();
        break;
    }

    case MotionEvent.ACTION_UP: {
        mActivePointerId = INVALID_POINTER_ID;
        break;
    }

    case MotionEvent.ACTION_CANCEL: {
        mActivePointerId = INVALID_POINTER_ID;
        break;
    }

    case MotionEvent.ACTION_POINTER_UP: {
        // Extract the index of the pointer that left the touch sensor
        final int pointerIndex = (action & MotionEvent.ACTION_POINTER_INDEX_MASK) 
                >> MotionEvent.ACTION_POINTER_INDEX_SHIFT;
        final int pointerId = ev.getPointerId(pointerIndex);
        if (pointerId == mActivePointerId) {
            // This was our active pointer going up. Choose a new
            // active pointer and adjust accordingly.
            final int newPointerIndex = pointerIndex == 0 ? 1 : 0;
            mLastTouchX = ev.getX(newPointerIndex);
            mLastTouchY = ev.getY(newPointerIndex);
            mActivePointerId = ev.getPointerId(newPointerIndex);
        }
        break;
    }
    }

    return true;
}