Android RelativeLayout 动态重置ALIGN_PARENT属性失效问题求助

• 复用了全局的parameters LayoutParams实例：addRule是累加规则而非替换，第一次点击setTop后parameters已经携带ALIGN_PARENT_TOP属性，后续点击setBottom时新增的ALIGN_PARENT_BOTTOM会和原有规则冲突，导致布局异常。
• reset变量的赋值逻辑无效：你先给testbox.layoutParams赋值reset，紧接着就赋值为修改后的parameters，reset的设置完全被覆盖，没有起到清除旧规则的作用。

你调用removeRule的写法本身没有问题，另外也可以用addRule(规则名称, 0)的方式实现等效的规则移除效果。推荐两种修复方式：

方式1：每次点击时创建新的LayoutParams实例，避免规则累加 #

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_margins_train)

    val testbox = findViewById<TextView>(R.id.testbox)
    val setTop = findViewById<TextView>(R.id.setTop)
    val setBottom = findViewById<TextView>(R.id.setBottom)

    setTop.setOnClickListener {
        // 每次创建新的LayoutParams实例
        val params = RelativeLayout.LayoutParams(heightBox.toInt(),widthBox.toInt())
        params.addRule(RelativeLayout.CENTER_HORIZONTAL)
        params.addRule(RelativeLayout.ALIGN_PARENT_TOP)
        testbox.layoutParams = params
    }
    setBottom.setOnClickListener {
        val params = RelativeLayout.LayoutParams(heightBox.toInt(),widthBox.toInt())
        params.addRule(RelativeLayout.CENTER_HORIZONTAL)
        params.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM)
        testbox.layoutParams = params
    }
}

方式2：以reset为基础修改规则，避免复用旧实例 #

如果需要保留reset的公共清除逻辑，可以每次基于reset复制新的实例再修改：

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_margins_train)

    val testbox = findViewById<TextView>(R.id.testbox)
    val setTop = findViewById<TextView>(R.id.setTop)
    val setBottom = findViewById<TextView>(R.id.setBottom)

    val reset = RelativeLayout.LayoutParams(heightBox.toInt(),widthBox.toInt()).apply { 
        removeRule(RelativeLayout.ALIGN_PARENT_END)
        removeRule(RelativeLayout.ALIGN_PARENT_TOP)
        removeRule(RelativeLayout.ALIGN_PARENT_BOTTOM)
        removeRule(RelativeLayout.ALIGN_PARENT_START)
        removeRule(RelativeLayout.CENTER_HORIZONTAL)
        removeRule(RelativeLayout.CENTER_VERTICAL)
    }

    setTop.setOnClickListener {
        // 基于reset复制新实例再添加规则
        val params = RelativeLayout.LayoutParams(reset)
        params.addRule(RelativeLayout.CENTER_HORIZONTAL)
        params.addRule(RelativeLayout.ALIGN_PARENT_TOP)
        testbox.layoutParams = params
    }
    setBottom.setOnClickListener {
        val params = RelativeLayout.LayoutParams(reset)
        params.addRule(RelativeLayout.CENTER_HORIZONTAL)
        params.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM)
        testbox.layoutParams = params
    }
}

内容的提问来源于stack exchange，提问作者Cerber