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

男娘i 2023-10-17 15:29 79阅读 0赞

**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：

![Center][]

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

[Center]: https://img-blog.csdn.net/20170901142935064?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvemhhbmdwaGls/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/Center