LinearGradient：線性漸變意思,這個也是繼承了Shader類,先看下它的建構函式：

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

對建構函式進行簡單的說明：

x0:起點x軸座標

y0:起點y軸座標

x1:終點x軸座標

y1:終點y軸座標

colors:顏色漸變值,這個和後面的positions值是對應的,

positions:顏色漸變百分比值

一張圖說明問題：

現在要實現我們今天要講的效果,程式碼如下：

package 
 
com.bitmapshaderdemo;
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.view.View;
 
/**
 * Created by admin on 2016/11/28.
 */
public class TextFlickerView extends View {
    private LinearGradient linearGradient;
    private String text = "今天杭州天氣真好";
    private Paint paint;
    private float strWidth;
    private Matrix matrix;
    private float translateX;
    private int signleTextWidth
 
;
    private int count = 1;//一次性跑多少個文字的個數
public TextFlickerView(Context context, AttributeSet attrs) {
        super(context, attrs);
init();
}
    private void init() {
        matrix = new Matrix();
paint = new Paint();
paint.setTextSize(30);
paint.setColor(Color.RED);
/**
         * (float x0, float y0, float x1, float y1, int[] colors, float[] positions, android.graphics.Shader.TileMode tile)
         */
strWidth =  paint.measureText(text);
signleTextWidth=(int) (count*strWidth/text.length());//計算一個文字的寬度
linearGradient = new LinearGradient(-signleTextWidth, 0, 0, 0, new int[]{0x22ffffff,0xffffffff,0x22ffffff}, new float[]{0,0.5f,1}, Shader.TileMode.CLAMP);//邊緣融合
paint.setShader(linearGradient);
}
    @Override
protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
canvas.drawText(text,0,100,paint);
translateX += signleTextWidth;//每次平移一個文字的寬度
if(translateX>=strWidth){
            signleTextWidth = -signleTextWidth;
}
        if(translateX==0){
            signleTextWidth = -signleTextWidth;
}
        //實現平移一個文字的寬度
matrix.setTranslate(translateX, 0);
linearGradient.setLocalMatrix(matrix);
postInvalidateDelayed(100);
}
}

ok!