Android View之对现有控件进行拓展实例

package com.xiong.demo1;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.LinearGradient;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.Shader;
import android.util.AttributeSet;
import android.widget.TextView;

/**
 * Created by xionglh on 2015/12/29.
 */
public class CustTextView extends TextView {


    private int mViewWith;
    private int mTranleate;
    private Paint mPaint;
    private LinearGradient mLinearGradient;
    private Matrix mMatrix;

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


    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        if (mViewWith == 0) {
            mViewWith = getMeasuredWidth();
            if (mViewWith > 0) {
                mPaint = getPaint();
                /**
                 * LinearGradient第一个和第二个参数表示颜色渐变的起点 第三、第四表示颜色渐变的终点 第五个参数表示渐变的颜色
                 * 第六个参数可以为空,表示坐标,值为0-1 new float[] {0.25f, 0.5f, 0.75f, 1 }
                 *如果这是空的，颜色均匀分布，沿梯度线
                 *  第七个表示平铺方式
                 * CLAMP重复最后一个颜色至最后
                 * MIRROR重复着色的图像水平或垂直方向已镜像方式填充会有翻转效果
                 *REPEAT重复着色的图像水平或垂直方向
                 */
                mLinearGradient = new LinearGradient(0, 0, mViewWith, 0,
                        new int[]{Color.parseColor("#7B68EE"), Color.parseColor("#FFC0CB"), Color.parseColor("#7B68EE")},
                        null, Shader.TileMode.MIRROR);
                mPaint.setShader(mLinearGradient);
                mMatrix = new Matrix();
            }
        }
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        if (mMatrix != null) {
            mTranleate += mViewWith / 14;
            if (mTranleate > 2 * mViewWith) {
                mTranleate = -mViewWith;
            }
            mMatrix.setTranslate(mTranleate, 0);
            mLinearGradient.setLocalMatrix(mMatrix);
            postInvalidateDelayed(100);
        }
    }
}