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
