Android官方DataBinding（十一）：对双向绑定之反向绑定的改进和简化

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Android官方DataBinding（十一）：对于双向绑定之反向绑定的改进和简化

本文接附录十文章，对附录十文章的代码和逻辑进行改进和简化，使得代码更易于阅读和理解，进一步清晰化文章十的下拉刷新实现代码和逻辑。

建立model：

package zhangphil.test;import android.databinding.BaseObservable;import android.databinding.ObservableBoolean;/** * Created by Phil on 2017/8/25. */public class ViewModel extends BaseObservable {    public final ObservableBoolean isRefreshing = new ObservableBoolean();}

写布局activity_main.xml：

<?xml version="1.0" encoding="utf-8"?><layout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:app="http://schemas.android.com/apk/res-auto">    <data>        <import type="android.view.View" />        <variable            name="model"            type="zhangphil.test.ViewModel" />    </data>    <LinearLayout        android:layout_width="match_parent"        android:layout_height="match_parent"        android:orientation="vertical">        <ProgressBar            android:layout_width="100dp"            android:layout_height="100dp"            android:layout_gravity="center_horizontal"            android:visibility="@{model.isRefreshing ? View.VISIBLE:View.GONE}" />        <TextView            android:layout_width="match_parent"            android:layout_height="50dp"            android:background="@android:color/holo_red_light"            android:gravity="center"            android:text="加载中..."            android:visibility="@{model.isRefreshing ? View.VISIBLE:View.GONE}" />        <zhangphil.test.PhilView            android:id="@+id/philview"            android:layout_width="match_parent"            android:layout_height="match_parent"            android:background="@android:color/holo_blue_light"            app:refreshing="@={model.isRefreshing}">            <LinearLayout                android:layout_width="match_parent"                android:layout_height="wrap_content"                android:orientation="vertical">                <TextView                    android:layout_width="match_parent"                    android:layout_height="150dp"                    android:gravity="center"                    android:text="z" />                <TextView                    android:layout_width="match_parent"                    android:layout_height="150dp"                    android:gravity="center"                    android:text="h" />                <TextView                    android:layout_width="match_parent"                    android:layout_height="150dp"                    android:gravity="center"                    android:text="a" />                <TextView                    android:layout_width="match_parent"                    android:layout_height="150dp"                    android:gravity="center"                    android:text="n" />                <TextView                    android:layout_width="match_parent"                    android:layout_height="150dp"                    android:gravity="center"                    android:text="g" />            </LinearLayout>        </zhangphil.test.PhilView>    </LinearLayout></layout>

自定义的双向绑定PhilView.java：

package zhangphil.test;import android.content.Context;import android.databinding.BindingAdapter;import android.databinding.InverseBindingAdapter;import android.databinding.InverseBindingListener;import android.support.v4.widget.NestedScrollView;import android.util.AttributeSet;import android.util.Log;/** * Created by Phil on 2017/8/25. */public class PhilView extends NestedScrollView {    private static final String TAG = "调试";    private static boolean isRefreshing = false;    public PhilView(Context context, AttributeSet attrs) {        super(context, attrs);    }    @BindingAdapter(value = "refreshing", requireAll = false)    public static void setRefreshing(PhilView view, boolean refreshing) {        if (isRefreshing == refreshing) {            //防止死循环            Log.d(TAG, "重复设置");            return;        } else {            Log.d(TAG, "setRefreshing " + refreshing);            isRefreshing = refreshing;        }    }    @InverseBindingAdapter(attribute = "refreshing", event = "refreshingAttrChanged")    public static boolean getRefreshing(PhilView view) {        return isRefreshing;    }    @BindingAdapter(value = {"refreshingAttrChanged"}, requireAll = false)    public static void setRefreshingAttrChanged(PhilView view, final InverseBindingListener inverseBindingListener) {        if (inverseBindingListener == null) {            Log.e(TAG, "InverseBindingListener为空!");        } else {            Log.d(TAG, "setRefreshingAttrChanged");            inverseBindingListener.onChange();        }    }}

测试的MainActivity.java：

package zhangphil.test;import android.databinding.DataBindingUtil;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.util.Log;import android.view.GestureDetector;import android.view.MotionEvent;import android.view.View;import zhangphil.test.databinding.ActivityMainBinding;public class MainActivity extends AppCompatActivity {    private final String TAG = "MainActivity调试";    private ViewModel mViewModel;    private ActivityMainBinding binding;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        final GestureDetector mGestureDetector = createGestureDetector();        binding = DataBindingUtil.setContentView(this, R.layout.activity_main);        mViewModel = new ViewModel();        binding.setModel(mViewModel);        binding.philview.setOnTouchListener(new View.OnTouchListener() {            @Override            public boolean onTouch(View view, MotionEvent motionEvent) {                mGestureDetector.onTouchEvent(motionEvent);                return false;            }        });    }    private GestureDetector createGestureDetector() {        // mGestureDetector用于监测用户在手机屏幕上的上滑和下滑事件。        GestureDetector mGestureDetector = new GestureDetector(this, new GestureDetector.SimpleOnGestureListener() {            @Override            public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {                //处于顶部且用户再下拉                if ((distanceY < 0) && (binding.philview.getScrollY() == 0)) {                    if (mViewModel.isRefreshing.get()) {                        Log.d(TAG, "加载中，请勿重复加载");                    } else {                        Log.d(TAG, "开始下拉刷新...");                        //执行下拉刷新/加载更多事务                        loadMore();                    }                }                return super.onScroll(e1, e2, distanceX, distanceY);            }        });        return mGestureDetector;    }    private void loadMore() {        new Thread(new Runnable() {            @Override            public void run() {                //通过设置布尔值改变View                mViewModel.isRefreshing.set(true);                try {                    //假设这里做了一个长时间的耗时操作                    Thread.sleep(3000);                } catch (InterruptedException e) {                    e.printStackTrace();                }                //通过设置布尔值改变View                mViewModel.isRefreshing.set(false);            }        }).start();    }}

代码运行结果，下拉刷新：

附录：
1，《Android官方DataBinding简例（一）》链接：http://blog.csdn.net/zhangphil/article/details/77322530
2，《Android官方DataBinding（二）：动态数据更新notifyPropertyChanged》链接：http://blog.csdn.net/zhangphil/article/details/77328688
3，《Android官方DataBinding（三）：RecyclerView 使用ViewDataBinding更新数据》链接：http://blog.csdn.net/zhangphil/article/details/77367432
4，《Android官方DataBinding（四）：BindingAdapter》链接：http://blog.csdn.net/zhangphil/article/details/77374211
5，《Android官方DataBinding（五）：ObservableMap，ObservableArrayMap》链接：http://blog.csdn.net/zhangphil/article/details/77448933
6，《Android官方DataBinding（六）： @= 操作符进行双向绑定》链接：http://blog.csdn.net/zhangphil/article/details/77454045
7，《Android官方DataBinding（七）：BindingMethods与BindingMethod》链接：http://blog.csdn.net/zhangphil/article/details/77479843
8，《Android官方DataBinding（八）：Lambda长表达式事件处理》链接：http://blog.csdn.net/zhangphil/article/details/77503013
9，《Android官方DataBinding（九）：反向绑定，View变化结果回写进数据模型中》链接：http://blog.csdn.net/zhangphil/article/details/77649256
10，《Android官方DataBinding（十）：双向绑定之基于InverseBindingAdapter的反向绑定》链接：http://blog.csdn.net/zhangphil/article/details/77767513

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