自定义Behavior（一）

跟谁手指移动的一个View

布局文件：

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="观察者View child"
        android:textColor="#333333"
        app:layout_behavior="com.czb.test.behavior.FollowBehavior" />

    <Button
        android:id="@+id/btn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:text="被观察View dependency（依赖者）" />

</android.support.design.widget.CoordinatorLayout>

Behavior的自定义

package com.czb.test.behavior;
import android.content.Context;
import android.support.design.widget.CoordinatorLayout;
import android.util.AttributeSet;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

/**
 * Created by czb365 on 2018/3/19.
 */

public class FollowBehavior extends CoordinatorLayout.Behavior<TextView> {//这里的泛型是child的类型，也就是观察者View

//这个构造方法比写
    public FollowBehavior(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    @Over
ride//关心那个View,也就是被观察者，也称依赖者
    public boolean layoutDependsOn(CoordinatorLayout parent, TextView child, View dependency) {
        return dependency instanceof Button;
    }

    @Override//当 dependency(Button)变化的时候，可以对child(TextView)进行操作
    public boolean onDependentViewChanged(CoordinatorLayout parent, TextView child, View dependency) {
        child.setX(dependency.getX() + 200);
        child.setY(dependency.getY() + 200);
        return true;
    }
}

activity代码

@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_test_move_view);
    findViewById(R.id.btn).setOnTouchListener(new View.OnTouchListener() {
        @Override
        public boolean onTouch(View v, MotionEvent event) {
            switch (event.getAction()) {
                case MotionEvent.ACTION_MOVE:
                    v.setX(event.getRawX() - v.getWidth() / 2);
                    v.setY(event.getRawY() - v.getHeight() / 2);
                    break;
            }
            return false;
        }
    });
}