android textview 文本展开收起-百家乐凯发k8

在界面上需要展示一个textview，默认超过4行则在末尾添加"展开"，用户点击展开文本后则完整显示文本，同时末尾添加“收起”。

先列出textview的布局

 <textview
     android:id="@ id/content"
     android:layout_width="match_parent"
     android:layout_height="wrap_content"
     android:layout_marginstart="20dp"
     android:layout_marginend="20dp"
     android:textcolor="#666666"
     android:linespacingextra="3dp"
     android:textsize="13sp"
     />

由于我们需要根据文本是否达到4行来做对应展示，很自然的想到要在textview布局完成之后再处理，此处设置onpredrawlistener

contenttextview.getviewtreeobserver()
               .addonpredrawlistener(new viewtreeobserver.onpredrawlistener() {
                   @override
                   public boolean onpredraw() {
                       contenttextview.getviewtreeobserver().removeonpredrawlistener(this);
                       expandtext();
                       return false;
                   }
               });

在expandtext中，如果文本布局超过4行，我们需要截取第四行，在文本后面预留展开的位置，最后通过设置span添加点击事件，收起功能类似。

    string expand = "[展开]";
    string collapse = "[收起]";
    private void expandtext() {
        charsequence text = contenttextview.gettext();
        int width = contenttextview.getwidth();
        textpaint paint = contenttextview.getpaint();
        layout layout = contenttextview.getlayout();
        int line = layout.getlinecount();
        if (line > 4) {
            int start = layout.getlinestart(3);
            int end = layout.getlinevisibleend(3);
            charsequence lastline = text.subsequence(start, end);
            float expandwidth = paint.measuretext(expand);
            float remain = width - expandwidth;
            charsequence ellipsize =
                    textutils.ellipsize(lastline,
                                        paint,
                                        remain,
                                        textutils.truncateat.end);
            clickablespan clickablespan = new clickablespan() {
                @override
                public void onclick(@nonnull view widget) {
                    collapsetext();
                }
            };
            spannablestringbuilder ssb = new spannablestringbuilder();
            ssb.append(text.subsequence(0, start));
            ssb.append(ellipsize);
            ssb.append(expand);
            ssb.setspan(new foregroundcolorspan(0xff7369f8),
                        ssb.length() - expand.length(), ssb.length(),
                        spanned.span_inclusive_exclusive);
            ssb.setspan(clickablespan,
                        ssb.length() - expand.length(), ssb.length(),
                        spanned.span_inclusive_exclusive);
            contenttextview.setmovementmethod(linkmovementmethod.getinstance());
            contenttextview.settext(ssb);
        }
    }
    private void collapsetext() {
        // 默认此时文本肯定超过行数了，直接在最后拼接文本
        clickablespan clickablespan = new clickablespan() {
            @override
            public void onclick(@nonnull view widget) {
                expandtext();
            }
        };
        spannablestringbuilder ssb = new spannablestringbuilder();
        ssb.append(bean.getmsg());
        ssb.append(collapse);
        ssb.setspan(new foregroundcolorspan(0xff7369f8),
                    ssb.length() - collapse.length(), ssb.length(),
                    spanned.span_inclusive_exclusive);
        ssb.setspan(clickablespan,
                    ssb.length() - collapse.length(), ssb.length(),
                    spanned.span_inclusive_exclusive);
        contenttextview.settext(ssb);
    }