大写和放大android中TextView的第一个字母

import android.graphics.Typeface;
import android.os.Bundle;
import android.text.SpannableString;
import android.text.style.RelativeSizeSpan;
import android.widget.TextView;
import androidx.appcompat.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        TextView textView = findViewById(R.id.textView);
        String text = textView.getText().toString();

        // 创建一个SpannableString对象
        SpannableString spannableString = new SpannableString(text);

        // 对第一个字母应用大写和放大效果
        if (text.length() > 0) {
            spannableString.setSpan(new RelativeSizeSpan(2.0f), 0, 1, SpannableString.SPAN_EXCLUSIVE_EXCLUSIVE);
            spannableString.setSpan(new TypefaceSpan("sans-serif-medium"), 0, 1, SpannableString.SPAN_EXCLUSIVE_EXCLUSIVE);
        }

        // 将处理后的SpannableString设置回TextView
        textView.setText(spannableString);
    }

    // 自定义TypefaceSpan类，用于设置字体样式
    private static class TypefaceSpan extends TypefaceSpan {
        private final Typeface newType;

        public TypefaceSpan(String family) {
            super(family);
            newType = Typeface.create(family, Typeface.NORMAL);
        }

        @Override
        public void updateDrawState(TextPaint ds) {
            applyCustomTypeFace(ds, newType);
        }

        @Override
        public void updateMeasureState(TextPaint paint) {
            applyCustomTypeFace(paint, newType);
        }

        private static void applyCustomTypeFace(Paint paint, Typeface tf) {
            int oldStyle;
            Typeface old = paint.getTypeface();
            if (old == null) {
                oldStyle = 0;
            } else {
                oldStyle = old.getStyle();
            }

            int fake = oldStyle & ~tf.getStyle();
            if ((fake & Typeface.BOLD) != 0) {
                paint.setFakeBoldText(true);
            }

            if ((fake & Typeface.ITALIC) != 0) {
                paint.setTextSkewX(-0.25f);
            }

            paint.setTypeface(tf);
        }
    }
}