Android 自定义设置文本字体间间距

自定义spacingTextView 继承TextView，代码如下:

public class SpacingTextView extends TextView {
private float letterSpacing = LetterSpacing.BIGGEST;
private CharSequence originalText = “”;

public SpacingTextView(Context context) {
    super(context);
}

public SpacingTextView(Context context, AttributeSet attrs){
    super(context, attrs);
    originalText = super.getText();
    applyLetterSpacing();
    this.invalidate();
}

public SpacingTextView(Context context, AttributeSet attrs, int defStyle){
    super(context, attrs, defStyle);
}

public float getLetterSpacing() {
    return letterSpacing;
}

public void setLetterSpacing(float letterSpacing) {
    this.letterSpacing = letterSpacing;
    applyLetterSpacing();
}

@Override
public void setText(CharSequence text, BufferType type) {
    originalText = text;
    applyLetterSpacing();
}

@Override
public CharSequence getText() {
    return originalText;
}

/**
 * 字距为任何字符串（技术上，一个简单的方法为CharSequence不使用）的TextView
 */
private void applyLetterSpacing() {
    if (this == null || this.originalText == null) return;
    StringBuilder builder = new StringBuilder();
    for(int i = 0; i < originalText.length(); i++) {
        String c = ""+ originalText.charAt(i);
        builder.append(c.toLowerCase());
        if(i+1 < originalText.length()) {
            builder.append("\u00A0");
        }
    }
    SpannableString finalText = new SpannableString(builder.toString());
    if(builder.toString().length() > 1) {
        for(int i = 1; i < builder.toString().length(); i+=2) {
            finalText.setSpan(new ScaleXSpan((letterSpacing+1)/10), i, i+1, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
        }
    }
    super.setText(finalText, BufferType.SPANNABLE);
}

public class LetterSpacing {
    public final static float NORMAL = 0;
    public final static float NORMALBIG = (float)0.025;
    public final static float BIG = (float)0.05;
    public final static float BIGGEST = (float)0.2;
}

}

代码中调用：
public class SpacingTextViewActivity extends BaseActivity {

private SpacingTextView spacingTextView;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_spacing_text_view);
    spacingTextView=findView(R.id.space_text);
    spacingTextView.setText(getResources().getString(R.string.space_test));
    spacingTextView.setLetterSpacing(ConvertUtils.dip2px(this,20));

}

}