Android官方DataBinding(十二):双向绑定之反向绑定的InverseBindingMethods改造和实现
在附录文章十、十一的基础上,使用InverseBindingMethod进行双向绑定和反向绑定操作。
以下是完整示例代码。
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>
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();
}
}
关键的PhilView.java:
package zhangphil.test;
import android.content.Context;
import android.databinding.InverseBindingListener;
import android.databinding.InverseBindingMethod;
import android.databinding.InverseBindingMethods;
import android.support.v4.widget.NestedScrollView;
import android.util.AttributeSet;
import android.util.Log;
/**
* Created by Phil on 2017/9/1.
*/
@InverseBindingMethods({@InverseBindingMethod(type = PhilView.class, attribute = "refreshing", event = "refreshingAttrChanged")})
public class PhilView extends NestedScrollView {
private String TAG = "调试";
private boolean isRefreshing = false;
public PhilView(Context context, AttributeSet attrs) {
super(context, attrs);
}
public void setRefreshing(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;
}
}
public boolean getRefreshing() {
return isRefreshing;
}
public void setRefreshingAttrChanged(InverseBindingListener inverseBindingListener) {
if (inverseBindingListener == null) {
Log.e(TAG, "InverseBindingListener为空!");
} else {
Log.d(TAG, "setRefreshingAttrChanged");
inverseBindingListener.onChange();
}
}
}
对比本篇文章的PhilView.java代码和附录十、十一的异同,最关键的地方是用InverseBindingMethod重新实现。InverseBindingMethod在注解定义的地方,有几点需要特别注意:
(1)InverseBindingMethod里面的event事件不是必须的,如果在InverseBindingMethod里面没有定义,那么Android系统自己会自动匹配查找。Android系统自动匹配查找的原则:根据定义的attribute值后面追加”AttrChanged”形成默认方法名进行匹配查找。比如,如果自己定义了attribute=”xxx”,那么Android系统自动会匹配查找xxxAttrChanged方法,该方法是set开头,那么就最终变成:setXxxAttrChanged
(2)如果开发者在event里面自己随意定义了一个方法名,那么必须严格一致确保类里面有这个方法,比如,如果用户在InverseBindingMethod的event里面任意定义了一个方法“abcdefg”,那么必须在该注解类有一个同名方法如setAbcdefg(),然后在这里面调用InverseBindingListener的onChange()。
(3)InverseBindingMethod中定义的attribute值,即为开发者想要和xml布局里面的app:xxx绑定的值。
(4)如果基于InverseBindingMethod,在绑定注解类里面get和set方法,后面的方法名即为attribute的值,举例,如果,attribute=”xxx”,那么set和get方法即为setXxx()和getXxx()。
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
11,《Android官方DataBinding(十一):对于双向绑定之反向绑定的改进和简化》链接:http://blog.csdn.net/zhangphil/article/details/77772671