• 建構函式

public LinearGradient(float x0, float y0, float x1, float y1,int color0, int color1, TileMode tile)

public LinearGradient(float x0, float y0, float x1, float y1,int colors[], float positions[], TileMode tile)

// color0 color1這是一個對兩個顏色的著色
// x0，y0 起始點 x1 ,y1 結束點
使用只需要 mPaint.setShader(shader);
下面用他實現一個漸變色的進度條帶有動畫效果

/**
 * 漸變顏色段
 */

private static final int[] SECTION_COLORS = {Color.RED, Color.GREEN, Color.BLUE};

private float maxCount = 100;

private float currentCount = 30;

private Paint mPaint;
private int mWidth, mHeight;

private RectF rectBg = new RectF();  // 外框背景
private RectF rectProgressBg = new RectF();//進度條
private LinearGradient shader;

public LinerProgressView(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    initView(context);
}

public LinerProgressView(Context context, AttributeSet attrs) {
    super(context, attrs);
    initView(context);
}

public LinerProgressView(Context context) {
    super(context);
    initView(context);
}

private void initView(Context context) {
    mPaint = new Paint();
}

@Override
protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
    super.onLayout(changed, left, top, right, bottom);
    mHeight = bottom - top;
    mWidth = right - left;
    rectBg.set(0, 0, mWidth, mHeight);
}

@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    if (shader == null) {
        shader = new LinearGradient(0, 0, mWidth, mHeight, SECTION_COLORS, null, Shader.TileMode.CLAMP);
    }
    mPaint.setShader(shader);
    mPaint.setAntiAlias(true);
    mPaint.setStyle(Paint.Style.STROKE);

    //繪製進度條外側邊框
    int round = mHeight * 1 / 3;
    canvas.drawRoundRect(rectBg, round, round, mPaint);

    //繪製進度條
    mPaint.setStyle(Paint.Style.FILL);
    float section = currentCount / maxCount;
    Log.i("currentCount","count:" + currentCount) ;
    int pl = (int) (mWidth * (section));
    rectProgressBg.set(0, 0, pl, mHeight);
    canvas.drawRoundRect(rectProgressBg, round, round, mPaint);
}

/*
 * 設定最大的進度值
 */
public void setMaxCount(float maxCount) {
    this.maxCount = maxCount;
}

/**
 * 設定當前的進度值
 * 2s 的漸變動畫 變加速
 */
public void setCurrentCount( float progress) {
    this.currentCount = progress > maxCount ? maxCount : progress;
    ValueAnimator animator = new ValueAnimator().ofFloat(0,progress);
    animator.setInterpolator( new AccelerateInterpolator());
    animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
        @Override
        public void onAnimationUpdate(ValueAnimator animation) {
            currentCount  = (float) animation.getAnimatedValue();
            postInvalidate();
        }
    });
    animator.setDuration(2000);
    animator.start();

}

public float getMaxCount() {
    return maxCount;
}

public float getCurrentCount() {
    return currentCount;
}
 

}
“`