Android超简单实现文字展开收起效果

目录

目录

效果展示

image

实现原理

原理很简单，需要用3个TextView，其中一个是展示文字的，一个是用来计算文字的行数，一个是用来展开和收起的：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
<!--    展示文字-->
    <TextView
        android:id="@+id/view_seemore_tvcontent"
        android:textColor="#000"
        android:maxLines="2"
        android:ellipsize="end"
        android:textSize="15sp"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>
<!--    占位置的隐藏，并且高度设置的很小，用来获取行数-->
    <TextView
        android:id="@+id/view_seemore_tvlinecount"
        android:textColor="#000"
        android:visibility="invisible"
        android:textSize="15sp"
        android:layout_width="match_parent"
        android:layout_height="1dp"/>
<!--    显示更多和收起-->
    <TextView
        android:id="@+id/view_seemore_tv_seemore"
        android:layout_marginTop="5dp"
        android:text="查看更多"
        android:textColor="#00f"
        android:visibility="gone"
        android:maxLines="2"
        android:ellipsize="end"
        android:textSize="15sp"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>
</LinearLayout>

然后需要在自定义控件的类中做相应的处理：

class SeeMoreView:FrameLayout {
    //是否展开和收起的标记
    private var mIsShowAll:Boolean = false
    constructor(context: Context) : this(context,null)
    constructor(context: Context, attrs: AttributeSet?) : this(context, attrs,0)
    constructor(context: Context, attrs: AttributeSet?, defStyleAttr: Int) : super(
        context,
        attrs,
        defStyleAttr
    ){
        View.inflate(context, R.layout.view_seemore,this)
        initListener()
    }
    private fun initListener() {
        //查看更多的点击事件
        view_seemore_tv_seemore.setOnClickListener {
            if(mIsShowAll){
                //这是收起的关键代码，将最大行数设置为你想展示的最小行数即可
                view_seemore_tvcontent.maxLines = 2
                view_seemore_tv_seemore.text = "查看更多"
            }else{
                //这是查看更多的关键代码，将最大行数设置一个大数即可
                view_seemore_tvcontent.maxLines = 20
                view_seemore_tv_seemore.text = "收起"
            }
            mIsShowAll = !mIsShowAll
        }
        //attachedToWindow之后执行操作
        post {
            //这里必须这样写，这是在attachedToWindow之后执行操作，否则获取行数会出问题
            Log.e("测试","OnLayout${view_seemore_tvlinecount.lineCount}")
            if(view_seemore_tvlinecount.lineCount>2){
                view_seemore_tv_seemore.visibility = View.VISIBLE
            }else{
                view_seemore_tv_seemore.visibility = View.GONE
            }
        }

    }
    /**
     * 设置文字
     */
    fun setText(text:String){
        //每次设置文字后都要进行重置
        view_seemore_tvcontent.text = text
        view_seemore_tvlinecount.text = text
        view_seemore_tv_seemore.text = "查看更多"
        view_seemore_tvcontent.maxLines = 2
        mIsShowAll = false
        if(view_seemore_tvlinecount.lineCount>2){
            view_seemore_tv_seemore.visibility = View.VISIBLE
        }else{
            view_seemore_tv_seemore.visibility = View.GONE
        }
    }
}

项目源码

https://github.com/myml666/SeeMore