Android官方DataBinding(十):双向绑定之基于InverseBindingAdapter的反向绑定
我给出一个简单例子,说明如何基于InverseBindingAdapter进行双向绑定中的反向绑定。
以一个经典的开发需求任务:下拉刷新。一般的下拉刷新,头部出现一个滚动的进度显示(ProgressBar)和一些文字提示,当下拉加载完毕后自动消失。
我写一个自定义view,继承自NestedScrollView,继承自NestedScrollView主要是为了利用NestedScrollView的下拉滚动事件。在这里面触发下拉刷新事件。
老规矩,先写一个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; private static InverseBindingListener mInverseBindingListener; 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) { Log.d(TAG, "setRefreshingAttrChanged"); if (inverseBindingListener == null) { view.setRefreshingListener(null); } else { mInverseBindingListener = inverseBindingListener; view.setRefreshingListener(mOnRefreshingListener); } } @Override protected void onScrollChanged(int x, int y, int oldx, int oldy) { super.onScrollChanged(x, y, oldx, oldy); if ((y < oldy) && y == 0) { if (isRefreshing) { Log.d(TAG, "正在刷新,请勿重复加载"); return; } else { longTimeTask(); } } } public void setRefreshingListener(OnRefreshingListener listener) { this.mOnRefreshingListener = listener; } public static abstract class OnRefreshingListener { public void startRefreshing() { isRefreshing = true; mInverseBindingListener.onChange(); } public void stopRefreshing() { isRefreshing = false; mInverseBindingListener.onChange(); } } private static OnRefreshingListener mOnRefreshingListener = new OnRefreshingListener() { @Override public void startRefreshing() { super.startRefreshing(); } @Override public void stopRefreshing() { super.stopRefreshing(); } }; private void longTimeTask() { new Thread(new Runnable() { @Override public void run() { mOnRefreshingListener.startRefreshing(); try { //假设这里做了一个长时间的耗时操作 Thread.sleep(5000); } catch (InterruptedException e) { e.printStackTrace(); } mOnRefreshingListener.stopRefreshing(); } }).start(); } }
测试的MainActivity.java:
package zhangphil.test; import android.databinding.DataBindingUtil; import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import zhangphil.test.databinding.ActivityMainBinding; public class MainActivity extends AppCompatActivity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); ActivityMainBinding binding = DataBindingUtil.setContentView(this, R.layout.activity_main); ViewModel vm = new ViewModel(); binding.setModel(vm); } }
代码运行结果初始化状态:
当下拉时候:
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