图片循环滚动控件ScrollingImageView

/**
* 可滚动的ImageView控件，使用startRolling(int) 或者 startRolling(Bitmap)启动滚动
* @author brian512
*/
public class ScrollingImageView extends View {

public final float SPEED_SLOW = 1f;
public final float SPEED_NORMAL = 3f;
public final float SPEED_FAST = 10f;

private Bitmap mBitmap;

private int mResourceID = 0;

private float mSpeed = SPEED_NORMAL;

private Rect clipBounds = new Rect(); // 用于保存边界信息

private float offset = 0; // 记录起始位置，需要拼接

private boolean mIsScrolling; // 标记是否开始滚动

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

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

public ScrollingImageView(Context context, AttributeSet attrs, int styleID) {
super(context, attrs, styleID);
//startScroll(R.drawable.loading_bg);
}

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
//        setMeasuredDimension(MeasureSpec.getSize(widthMeasureSpec), heightMeasureSpec);
}

@Override
public void onDraw(Canvas canvas) {
super.onDraw(canvas);
if (canvas == null) {
return;
}
Bitmap bitmap = getBitmap();
if (bitmap == null || bitmap.isRecycled()) {
return;
}
canvas.getClipBounds(clipBounds);

int width = bitmap.getWidth();
while (offset <= -width) {
offset += width;
}
float left = offset;

while (left < clipBounds.width()) {
canvas.drawBitmap(bitmap, getBitmapLeft(width, left), 0, null);
left += width;
}

if (mIsScrolling && mSpeed != 0) {
offset -= Math.abs(mSpeed);
postInvalidateOnAnimation();
}
}

private Bitmap getBitmap() {
if (mBitmap == null) {
mBitmap = BitmapFactory.decodeResource(getResources(), mResourceID);
}

return mBitmap;
}

private float getBitmapLeft(float layerWidth, float left) {
if (mSpeed < 0) {
return clipBounds.width() - layerWidth - left;
} else {
return left;
}
}

/**
* 开始滚动
*/
public void startScroll(int imageID) {
if (imageID <= 0) {
return;
}
mResourceID = imageID;
start();
}

/**
* 开始滚动
*/
public void startScroll(Bitmap bitmap) {
if (bitmap == null || bitmap.isRecycled()) {
return;
}
mBitmap = bitmap;
start();
}

private void start() {
if (!mIsScrolling) {
mIsScrolling = true;
postInvalidateOnAnimation();
}
}

/**
* 停止滚动
*/
public void stop() {
if (mIsScrolling) {
mIsScrolling = false;
invalidate();
}
}

/**
* 设置滚动速度
* @param speed 速度，默认为 SPEED_NORMAL = 3f
*/
public void setSpeed(float speed) {
this.mSpeed = speed;
if (mIsScrolling) {
postInvalidateOnAnimation();
}
}

/**
* 获取滚动速度
* @return
*/
public float getSpeed() {
return mSpeed;
}

/**
* 是否在滚动
* @return
*/
public boolean getIsScrolling() {
return mIsScrolling;
}

}