android 蒙版图片带拖动_在Android中通过在图片上拖动一个圆圈在图...
我从问题PorterduffXfermode: Clear a section of a bitmap中使用了有用的输入.在下面的示例中,触摸区域变为“透明”,可以观察up_image下面的down_image部分(这两个图像都是资源中的jpg drawable).
基本上有两种可能的实现：
>禁用图形的硬件加速,这会使PorterDuff.Mode.CLEAR使视图透明(有关硬件加速效果的更多详细信息,请参见here)：
活动：
public class MyActivity extends Activity {
/** Overlay image */
private DrawingView mDrawingView = null;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
final RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,
ViewGroup.LayoutParams.MATCH_PARENT);
// Create the view for the xfermode test
mDrawingView = new DrawingView(this);
params.addRule(RelativeLayout.CENTER_IN_PARENT);
mDrawingView.setLayoutParams(params);
final RelativeLayout relativeLayout = new RelativeLayout(this);
relativeLayout.setBackgroundResource(R.drawable.down_image);
relativeLayout.addView(mDrawingView);
// Main part of the implementation - make layer drawing software
if (android.os.Build.VERSION.SDK_INT >= 11) {
mDrawingView.setLayerType(View.LAYER_TYPE_SOFTWARE, null);
}
// Show the layout with the test view
setContentView(relativeLayout);
}
}
DrawingView：
/**
* View which makes touch area transparent
*/
public class DrawingView extends View {
/** Paint to clear touch area */
private Paint mClearPaint = null;
/** Main bitmap */
private Bitmap mBitmap = null;
/** X coordinate of touch circle */
private int mXTouch = -1;
/** Y coordinate of touch circle */
private int mYTouch = -1;
/** Radius of touch circle */
private int mRadius = 0;
/**
* Default constructor
*
* @param ct {@link Context}
*/
public DrawingView(final Context ct) {
super(ct);
// Generate bitmap used for background
mBitmap = BitmapFactory.decodeResource(ct.getResources(), R.drawable.up_image);
// Generate array of paints
mClearPaint = new Paint();
mClearPaint.setARGB(255, 255, 255, 0);
mClearPaint.setStrokeWidth(20);
mClearPaint.setStyle(Paint.Style.FILL);
// Set all transfer modes
mClearPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
mRadius = getResources().getDimensionPixelSize(R.dimen.radius);
}
@Override
public void onDraw(final Canvas canv) {
// Background colour for canvas
canv.drawColor(Color.argb(255, 0, 0, 0));
// Draw the bitmap leaving small outside border to see background
canv.drawBitmap(mBitmap, null, new RectF(0, 0, getMeasuredWidth(), getMeasuredHeight()), null);
// Loop, draws 4 circles per row, in 4 rows on top of bitmap
// Drawn in the order of mClearPaint (alphabetical)
if (mXTouch > 0 && mYTouch > 0) {
canv.drawCircle(mXTouch, mYTouch, mRadius, mClearPaint);
}
}
@Override
public boolean onTouchEvent(final MotionEvent event) {
boolean handled = false;
// get touch event coordinates and make transparent circle from it
switch (event.getActionMasked()) {
case MotionEvent.ACTION_DOWN:
case MotionEvent.ACTION_MOVE:
mXTouch = (int) event.getX();
mYTouch = (int) event.getY();
// TODO: Note, in case of large scene it's better not to use invalidate without rectangle specified
invalidate();
handled = true;
break;
case MotionEvent.ACTION_UP:
case MotionEvent.ACTION_POINTER_UP:
case MotionEvent.ACTION_CANCEL:
mXTouch = -1;
mYTouch = -1;
// TODO: Note, in case of large scene it's better not to use invalidate without rectangle specified
invalidate();
handled = true;
break;
default:
// do nothing
break;
}
return super.onTouchEvent(event) || handled;
}
}
>采用此solution,但看起来它取决于Android版本,因为建议的解决方案根本不适用于我的4.2设备.