1.效果
image.png
2.根据效果，分析如实现
效果是，文字自做导游逐渐变色，用TextView无法实现，这里采用自定义View，让他继承自TextView，这样的话，就不需要再重写onMeasure()方法，这里，我们只需要自定义两张字体颜色（默认颜色和要变色的颜色就可）。
3.代码实现
3.1 自定义属性
在valuse目录下创建attrs.xml文件，在里面创建自定义属性
<declare-styleable name="ColorTrackTextView">
<attr name="cmOriginTextColor" format="color"></attr>
<attr name="cmChangeTextColor" format="color"></attr>
</declare-styleable>
3.2 在布局中调用
<com.test.cmviewdemo.ColorTrackTextView
android:text="@string/app_name"
android:id="@+id/main_TrackTextView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_margin="10dp"
android:textSize="22sp"
app:cmChangeTextColor="@color/colorAccent"
app:cmOriginTextColor="@color/colorPrimary" />
3.3 创建自定义View类，并继承自TextView
public class ColorTrackTextView extends AppCompatTextView {
public ColorTrackTextView(Context context) {
this(context,null);
}
public ColorTrackTextView(Context context, @Nullable AttributeSet attrs) {
this(context, attrs,0);
}
public ColorTrackTextView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
}
}
3.4 创建画笔（在构造方法中调用initPaint()方法，创建画笔）
private Paint cmOriginTextPaint;
private Paint cmChangeTextPaint;
private void initPaint(Context context, AttributeSet attrs) {
//获取自定义属性
TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.ColorTrackTextView);
int cmOriginTextColor = typedArray.getColor(R.styleable.ColorTrackTextView_cmOriginTextColor, getTextColors().getDefaultColor());
int cmChangeTextColor = typedArray.getColor(R.styleable.ColorTrackTextView_cmChangeTextColor, getTextColors().getDefaultColor());
typedArray.recycle();
//根据自定义的颜色来创建画笔
cmOriginTextPaint = getTextPaintByColor(cmOriginTextColor);
cmChangeTextPaint = getTextPaintByColor(cmChangeTextColor);
}
3.5 重写onDray()方法，从新绘制Text
/**
* 根据自定义画笔，重写onDray()方法，重写绘制
* @param canvas
*/
@Override
protected void onDraw(Canvas canvas) {
//根据当前进度，获取当前中间值
int middle = (int) (cmCurrentProgress * getWidth());
//根据朝向，绘制TextView
if(Directory.LEFT_TO_RIGHT == cmCurrentDirectory){
//当前朝向为 从左到右
drawText(canvas,cmChangeTextPaint,0,middle);
drawText(canvas,cmOriginTextPaint,middle,getWidth());
}else{
//当前朝向 从右到左
drawText(canvas,cmChangeTextPaint,getWidth() - middle,getWidth());
drawText(canvas,cmOriginTextPaint,0,getWidth()-middle);
}
}
/**
* 绘制TextView
* @param canvas
* @param textPaint
* @param start
* @param end
*/
private void drawText(Canvas canvas, Paint textPaint, int start, int end) {
//保存画布状态
canvas.save();
Rect rect = new Rect(start,0,end,getHeight());
canvas.clipRect(rect);
//获取文字
String text = getText().toString();
Rect bounds = new Rect();
textPaint.getTextBounds(text,0,text.length(),bounds);
//获取字体的宽度
int x = getWidth()/2 - bounds.width()/2;
//获取基线
Paint.FontMetricsInt fontMetricsInt = textPaint.getFontMetricsInt();
int dy = (fontMetricsInt.bottom - fontMetricsInt.top)/2 - fontMetricsInt.bottom;
int baseLine = getHeight()/2 + dy;
canvas.drawText(text,x,baseLine,textPaint);
//释放画布状态，既恢复Canvas旋转，缩放等之后的状态。
canvas.restore();
}
4
Github Demo 地址
https://github.com/hualianrensheng/CMViewDemo
