我是一名Android初学者，有一个比较简单的问题。我创建了一个自定义视图，然后通过xml将其注入到另一个布局中。我想让这个自定义视图的背景透明。
我的自定义视图在xml中的注入：
<com.sagar.utils.ConnectDotsView
android:id="@+id/connect_dots_view"
android:layout_width="match_parent"
android:layout_height="match_parent" />
这是自定义 View 的代码：
public class ConnectDotsView extends View {
private Bitmap mBitmap;
private Canvas mCanvas;
private Path mPath;
private Paint mPaint;
private static final int TOUCH_TOLERANCE_DP = 24;
private static final int BACKGROUND = 0xFFDDDDDD;
// Points to be connected.
private List<Point> mPoints = new ArrayList<>();
private int mLastPointIndex = 0;
private int mTouchTolerance;
private boolean isPathStarted = false;
CompleteListener completeListener;
public ConnectDotsView(Context context) {
super(context);
mCanvas = new Canvas();
mPath = new Path();
initPaint();
}
public interface CompleteListener {
void onCompleteListener();
}
public void setOnCompleteListener(CompleteListener listener) {
completeListener = listener;
}
public ConnectDotsView(Context context, AttributeSet attrs) {
super(context, attrs);
mCanvas = new Canvas();
mPath = new Path();
initPaint();
}
public ConnectDotsView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
mCanvas = new Canvas();
mPath = new Path();
initPaint();
}
public void clear() {
mBitmap = Bitmap.createBitmap(getWidth(), getHeight(), Bitmap.Config.ARGB_8888);
mBitmap.eraseColor(BACKGROUND);
mCanvas.setBitmap(mBitmap);
invalidate();
}
@Override
protected void onSizeChanged(int width, int height, int oldWidth, int oldHeight) {
super.onSizeChanged(width, height, oldWidth, oldHeight);
clear();
}
@Override
protected void onDraw(Canvas canvas) {
canvas.drawColor(BACKGROUND);
canvas.drawBitmap(mBitmap, 0, 0, null);
canvas.drawPath(mPath, mPaint);
mPaint.setColor(Color.parseColor("#56CBF9"));
// TODO remove if you don't want points to be visible.
for (Point point : mPoints) {
canvas.drawPoint(point.x, point.y, mPaint);
mPaint.setColor(Color.BLACK);
}
}
@Override
public boolean onTouchEvent(MotionEvent event) {
float x = event.getX();
float y = event.getY();
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
touch_start(x, y);
invalidate();
break;
case MotionEvent.ACTION_MOVE:
touch_move(x, y);
invalidate();
break;
case MotionEvent.ACTION_UP:
touch_up(x, y);
invalidate();
break;
}
return true;
}
private void touch_start(float x, float y) {
if (checkPoint(x, y, mLastPointIndex)) {
mPath.reset();
// User starts from given point so path can be drawn.
isPathStarted = true;
} else {
// User starts move from point which does not belong to mPoints list
isPathStarted = false;
}
}
private void touch_move(float x, float y) {
if (isPathStarted) {
mPath.reset();
Point point = mPoints.get(mLastPointIndex);
mPath.moveTo(point.x, point.y);
if (checkPoint(x, y, mLastPointIndex + 1)) {
point = mPoints.get(mLastPointIndex + 1);
mPath.lineTo(point.x, point.y);
mCanvas.drawPath(mPath, mPaint);
mPath.reset();
++mLastPointIndex;
} else {
int positionIndex = mLastPointIndex + 1;
if (positionIndex >= mPoints.size()) {
completeListener.onCompleteListener();
} else {
mPath.lineTo(x, y);
}
}
}
}
private void touch_up(float x, float y) {
mPath.reset();
if (checkPoint(x, y, mLastPointIndex + 1) && isPathStarted) {
// Move finished at valid point so I draw whole line.
// That's the start point of current line segment.
Point point = mPoints.get(mLastPointIndex);
mPath.moveTo(point.x, point.y);
// And that's the end point.
point = mPoints.get(mLastPointIndex + 1);
mPath.lineTo(point.x, point.y);
mCanvas.drawPath(mPath, mPaint);
mPath.reset();
// Increment point index.
++mLastPointIndex;
isPathStarted = false;
}
}
/**
* Checks if user touch point with some tolerance
*/
private boolean checkPoint(float x, float y, int pointIndex) {
if (pointIndex >= mPoints.size()) {
// All dots already connected.
return false;
}
Point point = mPoints.get(pointIndex);
if (x > (point.x - mTouchTolerance) && x < (point.x + mTouchTolerance)) {
if (y > (point.y - mTouchTolerance) && y < (point.y + mTouchTolerance)) {
return true;
}
}
return false;
}
/**
* Sets up paint attributes.
*/
private void initPaint() {
mPaint = new Paint();
mPaint.setAntiAlias(true);
mPaint.setDither(true);
mPaint.setColor(Color.BLACK);
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setStrokeJoin(Paint.Join.ROUND);
mPaint.setStrokeCap(Paint.Cap.ROUND);
mPaint.setStrokeWidth(12);
mTouchTolerance = dp2px(TOUCH_TOLERANCE_DP);
}
/**
* Converts dpi units to px
*
* @param dp
* @return
*/
private int dp2px(int dp) {
Resources r = getContext().getResources();
float px = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dp, r.getDisplayMetrics());
return (int) px;
}
public void setPaint(Paint paint) {
this.mPaint = paint;
}
public Bitmap getBitmap() {
return mBitmap;
}
public List<Point> getPoints() {
return mPoints;
}
public void setPoints(List<Point> points) {
mLastPointIndex = 0;
this.mPoints = points;
}
}
我希望将上述自定义视图的背景设置为透明。我该如何通过xml或代码实现呢？
谢谢您的提前帮助。