自定义textview产生渐变色

 1 package sowell.oracle.com.viewdraw;
 2 
 3 import android.content.Context;
 4 import android.graphics.Canvas;
 5 import android.graphics.Color;
 6 import android.graphics.LinearGradient;
 7 import android.graphics.Matrix;
 8 import android.graphics.Paint;
 9 import android.graphics.Shader;
10 import android.util.AttributeSet;
11 import android.widget.TextView;
12 
13 
14 /**
15  * Created by 94965 on 2017/11/10.
16  */
17 
18 public class MyTextView extends TextView {
19 
20 
21 
22     public int mViewWidth;   //记录TextView的宽度
23     public Paint paint1;
24     public Paint paint2;
25     public Paint paint;
26     public LinearGradient linearGradient;      //线性渲染器
27     public Matrix matrix;
28     public int translate;
29 
30     public void init(){
31         mViewWidth=0;
32         paint1=new Paint();
33         paint2=new Paint();
34         paint=new Paint();
35     }
36 
37 
38     public MyTextView(Context context, AttributeSet attrs,int defStyle){
39         super(context,attrs,defStyle);
40     }
41 
42     public MyTextView(Context context,AttributeSet attrs){
43         super(context,attrs);
44     }
45 
46     public MyTextView(Context context){
47         super(context);
48     }
49 
50     @Override
51     protected void onSizeChanged(int w, int h, int oldw, int oldh) {
52         super.onSizeChanged(w, h, oldw, oldh);
53         if(mViewWidth==0){
54             mViewWidth=getMeasuredWidth();
55             if(mViewWidth>0){
56                 paint=getPaint();
57                 //定义渐变区域的大小
58                 linearGradient=new LinearGradient(
59                         0,
60                         0,
61                         mViewWidth,
62                         0,
63                         new int[]{
64                                 Color.BLUE,0xfffffff,
65                                 Color.BLUE
66                         },
67                         null,
68                         Shader.TileMode.CLAMP
69                 );
70                 paint.setShader(linearGradient);
71                 matrix=new Matrix();
72             }
73         }
74     }
75 
76     @Override
77     protected void onDraw(Canvas canvas) {
78         super.onDraw(canvas);
79         if(matrix!=null){
80             translate+=mViewWidth/5;
81             if(translate>2*mViewWidth){
82                 translate=-mViewWidth;
83             }
84             matrix.setTranslate(translate,0);
85             linearGradient.setLocalMatrix(matrix);
86             postInvalidateDelayed(100);
87         }
88     }
89 }