效果图

废话不多说，先看效果图：

开发环境

我发现很多人写文章都没写开发环境，抄过去经常也要改不少东西。所以从我做起，我先写一下开发环境。
Android Studio 3.4.2
SDK：Android Q API level29

修改字体

我们先讲讲怎么修改字体。
我只讲我用的方法。安卓默认只有4种字体，我要导入自定义的字体。方法如下：
在app/src/main下新建一个assets文件夹，在assets文件夹里面再新建一个fonts文件夹。将自定义的字体放进去到fonts下面，可以放进去otf格式和ttf格式的字体。
AS3.4.2可以右键新建出fonts文件夹：
new→folder→font resources folder
然后在设置layout.xml

<TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/title1"
            android:id="@+id/title1" />

然后在mainActivity里面设置字体：

public class MainActivity extends AppCompatActivity {
    private TextView title1;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        title1 = findViewById(R.id.title1);
        // 设置字体
        Typeface typeface = Typeface.createFromAsset(getAssets(),"fonts/MarkerScratch-Regular-2.ttf");
        title1.setTypeface(typeface);
        }
    }

"fonts/MarkerScratch-Regular-2.ttf"为我在fonts目录下放置的字体，自行改为自己要自定义的字体即可。

更详细的换字体的方法请查看Android TextView更换字体

字体渐变

效果图如下：

新建一个GradientColorTextView类：

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

/**
 * Created by Haron on 2017/11/14.
 */

public class GradientColorTextView extends TextView {

    private LinearGradient mLinearGradient;
    private Paint mPaint;
    private int mViewWidth = 0;
    private Rect mTextBound = new Rect();

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

    @Override
    protected void onDraw(Canvas canvas) {
        mViewWidth = getMeasuredWidth();
        mPaint = getPaint();
        String mTipText = getText().toString();
        mPaint.getTextBounds(mTipText, 0, mTipText.length(), mTextBound);
        mLinearGradient = new LinearGradient(0, 0, mViewWidth, 0,
                new int[]{0xFFFFEABA, 0xFFBE8B49},
                null, Shader.TileMode.REPEAT);
        mPaint.setShader(mLinearGradient);
        canvas.drawText(mTipText, getMeasuredWidth() / 2 - mTextBound.width() / 2, getMeasuredHeight() / 2 + mTextBound.height() / 2, mPaint);
    }
}

修改layout.xml：

<com.example.myTextView.GradientColorTextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/title1"
            android:id="@+id/title1"
            android:layout_marginLeft="10dp"
            android:textSize="50sp"
             />

引用路径com.example.myTextView.GradientColorTextView改为自己的路径，AS都有提示的。
引用自Android Textview实现文字颜色渐变效果

字体动态渐变

经过上一步应该就已经实现了在两种颜色之间的字体渐变了。接下来就要把颜色改成动态的了。
修改GradientColorTextView.java

package com.example.myTextView;

import android.animation.ValueAnimator;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.LinearGradient;
import android.graphics.Paint;
import android.graphics.Rect;
import android.graphics.Shader;
import android.util.AttributeSet;
import android.widget.TextView;

/**
 * Created by Haron on 2017/11/14.
 */
/**
 * Edit by Negineko on 2019/08/23.
 */

public class GradientColorTextView extends TextView {

    private LinearGradient mLinearGradient;
    private Paint mPaint;
    private int mViewWidth = 0;
    private Rect mTextBound = new Rect();
    private int[] color = {0xFFFFEABA, 0xFFBE8B49}; // 渐变色范围
    private ValueAnimator leftAnimator,rightAnimator;
    private boolean isAnimation = true; // 设置渐变色动态变化

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

    public void setIsAnimation(boolean isAnimation){
        this.isAnimation = isAnimation;
    }

    public void setColor(int[] color){
        this.color = color;
        invalidate();
    }

    @Override
    protected void onDraw(Canvas canvas) {
        mViewWidth = getMeasuredWidth();
        mPaint = getPaint();
        String mTipText = getText().toString();
        mPaint.getTextBounds(mTipText, 0, mTipText.length(), mTextBound);
        leftAnimator = ValueAnimator.ofInt(0, color[0]);
        rightAnimator = ValueAnimator.ofInt(0, color[1]);
        // 自动更新view
        invalidate();
        // 设置是否有动画
        if (isAnimation){
            color[0] = color[0]-100;
            color[1] = color[1]-100;
        }
        // 设置颜色渐变
        mLinearGradient = new LinearGradient(0, 0, mViewWidth, 0,
                color,
                null, Shader.TileMode.REPEAT);
//        System.out.println(color.toString());
        mPaint.setShader(mLinearGradient);
        canvas.drawText(mTipText, getMeasuredWidth() / 2 - mTextBound.width() / 2, getMeasuredHeight() / 2 + mTextBound.height() / 2, mPaint);
    }
}

给出demo下载地址
myTextViewDemo