android 图文混排图片居中实现

前言

android的图文混排是基于SpannableString中设置ImageSpan实现的，系统默认的ImageSpan只有两种排列方式：

 底部对齐
     */
    public static final int ALIGN_BOTTOM = 0;
    
    /**
     基线对齐
     */
    public static final int ALIGN_BASELINE = 1;

设计有时候需要图片基于文字中心对齐，这里就需要继承ImageSpan重写draw方法。

代码

public class CenterAlignImageSpan extends ImageSpan {
    public CenterAlignImageSpan(Drawable d) {
        super(d);
    }

    @Override
    public void draw(Canvas canvas, CharSequence text, int start, int end, float x, int top, int y, int bottom, Paint paint) {
        Drawable drawable = getDrawable();
        Paint.FontMetricsInt fm = paint.getFontMetricsInt();
        int transY = (y + fm.descent + y + fm.ascent) / 2 - drawable.getBounds().bottom / 2;
        canvas.save();
        canvas.translate(x, transY);
        drawable.draw(canvas);
        canvas.restore();
    }
}

测试代码如下：

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        TextView textView = findViewById(R.id.test_tx);
        String str = "this is a test";
        SpannableString spanString = new SpannableString(str);
        Drawable drawable = this.getResources().getDrawable(R.drawable.test);
        drawable.setBounds(0, 0, 40, 40);   //设置图片显示区域大小
        CenterAlignImageSpan imageSpan = new CenterAlignImageSpan(drawable);
        spanString.setSpan(imageSpan, spanString.length() - 3, spanString.length(), Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
        SpannableStringBuilder builder = new SpannableStringBuilder();
        builder.append("测试： ");
        builder.append(spanString);
        textView.setText(builder);
    }