自定义textview产生渐变色

package sowell.oracle.com.viewdraw;

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 94965 on 2017/11/10.
 */

public class MyTextView extends TextView {



    public int mViewWidth;   //记录TextView的宽度
    public Paint paint1;
    public Paint paint2;
    public Paint paint;
    public LinearGradient linearGradient;      //线性渲染器
    public Matrix matrix;
    public int translate;

    public void init(){
        mViewWidth=0;
        paint1=new Paint();
        paint2=new Paint();
        paint=new Paint();
    }


    public MyTextView(Context context, AttributeSet attrs,int defStyle){
        super(context,attrs,defStyle);
    }

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

    public MyTextView(Context context){
        super(context);
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        if(mViewWidth==0){
            mViewWidth=getMeasuredWidth();
            if(mViewWidth>0){
                paint=getPaint();
                //定义渐变区域的大小
                linearGradient=new LinearGradient(
                        0,
                        0,
                        mViewWidth,
                        0,
                        new int[]{
                                Color.BLUE,0xfffffff,
                                Color.BLUE
                        },
                        null,
                        Shader.TileMode.CLAMP
                );
                paint.setShader(linearGradient);
                matrix=new Matrix();
            }
        }
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        if(matrix!=null){
            translate+=mViewWidth/5;
            if(translate>2*mViewWidth){
                translate=-mViewWidth;
            }
            matrix.setTranslate(translate,0);
            linearGradient.setLocalMatrix(matrix);
            postInvalidateDelayed(100);
        }
    }
}