参考自 Android 群英传

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1.设置渐变色画笔

    private void iniView(){
        mPaint = new Paint();
        mPaint.setColor(Color.RED);
        mPaint.setStyle(Paint.Style.FILL);
        mRectCount = 12;
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        mWidth = getWidth();
        mRectHeight = getHeight();
        mRectWidth = (int) (mWidth * 0.6 / mRectCount);
        mLinearGradient = new LinearGradient(
                0,
                0,
                mRectWidth,
                mRectHeight,
                Color.WHITE,
                Color.RED,
                Shader.TileMode.CLAMP);
        mPaint.setShader(mLinearGradient);
    }

2.重写 onDraw() 方法

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        for ( int i = 0 ; i < mRectCount ; i++ ){
            mRandom = Math.random();
            currentHeight = (float) (mRectHeight * mRandom);
            canvas.drawRect(
                    (float)(mWidth*0.4/2 + mRectWidth*i + offset),
                    currentHeight,
                    (float)(mWidth*0.4/2 + mRectWidth*(i+1)),
                    mRectHeight,
                    mPaint);
        }
        postInvalidateDelayed(300);
    }

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完整代码

public class UI_3_6_3_2 extends View {

    /*
    数据成员
     */
    private int mRectCount;//小矩形的数目
    private int mWidth;
    private int mRectWidth;//每个小矩形的宽度
    private int mRectHeight;//每个小矩形的高度
    private int offset = 5;//每个小矩形之间的偏移量
    private float currentHeight;


    /*
    LinearGradient
     */
    private LinearGradient mLinearGradient;//产生渐变效果

    /*
    Paint
     */
    private Paint mPaint;//绘制小矩形的画笔
    private double mRandom;

    public UI_3_6_3_2(Context context) {
        super(context);
        iniView();
    }

    public UI_3_6_3_2(Context context, AttributeSet attrs) {
        super(context, attrs);
        iniView();
    }

    public UI_3_6_3_2(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        iniView();
    }

    private void iniView(){
        mPaint = new Paint();
        mPaint.setColor(Color.RED);
        mPaint.setStyle(Paint.Style.FILL);
        mRectCount = 12;
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        mWidth = getWidth();
        mRectHeight = getHeight();
        mRectWidth = (int) (mWidth * 0.6 / mRectCount);
        mLinearGradient = new LinearGradient(
                0,
                0,
                mRectWidth,
                mRectHeight,
                Color.WHITE,
                Color.RED,
                Shader.TileMode.CLAMP);
        mPaint.setShader(mLinearGradient);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        for ( int i = 0 ; i < mRectCount ; i++ ){
            mRandom = Math.random();
            currentHeight = (float) (mRectHeight * mRandom);
            canvas.drawRect(
                    (float)(mWidth*0.4/2 + mRectWidth*i + offset),
                    currentHeight,
                    (float)(mWidth*0.4/2 + mRectWidth*(i+1)),
                    mRectHeight,
                    mPaint);
        }
        postInvalidateDelayed(300);
    }

}