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

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