自定义控件的使用方法

1.自定义一个派生的view或者viewgroup类的控件时,必须实现一个构造函数,有三个构造函数需要实现

如:

   public CustomView(Context context) {
        super(context);
       
    }
    public CustomView(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
       
    }
    public CustomView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {//xml引用控件,必须实现这个构造函数
        super(context, attrs, defStyleAttr);
       
    }

动态添加控件

        /**
         * layout_wight定义
         */
//        LinearLayout rootView = (LinearLayout) findViewById(R.id.root);
//        CustomView customView = new CustomView(this);
//        LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.MATCH_PARENT);
//        layoutParams.weight = 1.0f;
//        rootView.addView(customView, layoutParams);


        /**
         * RelativeLayout添加布局规则
         */
//        RelativeLayout rootView = (RelativeLayout) findViewById(R.id.root);
//        CustomView customView = new CustomView(this);
//        RelativeLayout.LayoutParams layoutParams = new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.MATCH_PARENT, RelativeLayout.LayoutParams.MATCH_PARENT);
//        layoutParams.addRule(RelativeLayout.RIGHT_OF, R.id.text);  //第一个参数是相对布局的布局属性,第二个参数是指相对哪个控件ID来布局
//        rootView.addView(customView, layoutParams);


        /**
         * setGravity使用
         */
        RelativeLayout rootView = (RelativeLayout) findViewById(R.id.root);
        RelativeLayout.LayoutParams layoutParams = new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.WRAP_CONTENT, 200);
        layoutParams.addRule(RelativeLayout.RIGHT_OF, R.id.text);

        Button button = new Button(this);
        button.setGravity(Gravity.TOP);
        button.setText("btn");
        rootView.addView(button, layoutParams);
        rootView.setGravity(Gravity.TOP | Gravity.CENTER_HORIZONTAL);

RelativeLayout比LinearLayout特殊,需要多设置相对属性在代码中动态设置,这些的方法是通过RelativeLayout.LayiutParams的addRule函数

public void addRule(int verb, int subject)// verb布局属性,subject根据哪个控件ID布局