Android官方DataBinding（九）：反向绑定，View变化结果回写进数据模型中
附录文章大部分是单向绑定：数据模型的变化，引起View的变化。那么现在实行一个简单的功能，View的变化结果，回写到数据模型里面去。
写一个ViewModel类，里面定义一个布尔isDisplay：
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 isDisplay = new ObservableBoolean();
}
我以这样一个例子说明，在一个自定义View里面增加一个自定义属性:display，该值是布尔类型，如果true，则显示该View，如果false，则不显示该View。
自定义PhilView.java：
package zhangphil.test;
import android.content.Context;
import android.databinding.BindingAdapter;
import android.databinding.InverseBindingAdapter;
import android.databinding.InverseBindingListener;
import android.util.AttributeSet;
import android.util.Log;
import android.view.View;
/**
* Created by Phil on 2017/8/25.
*/
public class PhilView extends View {
private static final String TAG = "调试";
private OnViewChangeListener mOnViewChangeListener;
public PhilView(Context context, AttributeSet attrs) {
super(context, attrs);
}
//继承自Android，该方法在Android的View的visibility变化时候回调
@Override
protected void onVisibilityChanged(View changedView, int visibility) {
super.onVisibilityChanged(changedView, visibility);
Log.d(TAG, "onVisibilityChanged");
if (mOnViewChangeListener != null) {
mOnViewChangeListener.onChange();
}
}
@BindingAdapter(value = "display", requireAll = false)
public static void setDisplay(PhilView view, boolean isDisplay) {
if (getDisplay(view) == isDisplay) {
//防止死循环
Log.d(TAG, "重复设置");
return;
} else {
Log.d(TAG, "setDisplay " + isDisplay);
view.setVisibility(isDisplay ? View.VISIBLE : View.INVISIBLE);
}
}
@InverseBindingAdapter(attribute = "display", event = "displayAttrChanged")
public static boolean getDisplay(PhilView view) {
Log.d(TAG, "getDisplay:" + view.getVisibility());
return view.getVisibility() == View.VISIBLE;
}
@BindingAdapter(value = {"displayAttrChanged"}, requireAll = false)
public static void setDisplayAttrChanged(PhilView view, final InverseBindingListener inverseBindingListener) {
Log.d(TAG, "setDisplayAttrChanged");
if (inverseBindingListener == null) {
view.setViewChangeListener(null);
Log.d(TAG, "setViewChangeListener(null)");
} else {
view.setViewChangeListener(new OnViewChangeListener() {
@Override
public void onChange() {
Log.d(TAG, "setDisplayAttrChanged -> onChange");
inverseBindingListener.onChange();
}
});
}
}
private interface OnViewChangeListener {
void onChange();
}
private void setViewChangeListener(OnViewChangeListener listener) {
this.mOnViewChangeListener = listener;
}
}
在activity_main.xml中的定义：
<?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">
<CheckBox
android:id="@+id/checkbox"
android:layout_width="50dp"
android:layout_height="50dp" />
<ImageView
android:layout_width="100dp"
android:layout_height="100dp"
android:src="@mipmap/ic_launcher_round"
android:visibility="@{checkbox.checked?View.VISIBLE:View.GONE}" />
<zhangphil.test.PhilView
android:id="@+id/philview"
android:layout_width="match_parent"
android:layout_height="200dp"
android:background="@android:color/holo_red_light"
app:display="@={model.isDisplay}" />
</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.View;
import zhangphil.test.databinding.ActivityMainBinding;
public class MainActivity extends AppCompatActivity {
private final String TAG = "调试的MainActivity";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
final ActivityMainBinding binding = DataBindingUtil.setContentView(this, R.layout.activity_main);
final ViewModel vm = new ViewModel();
binding.setModel(vm);
//数据模型的变化将控制View的显示
vm.isDisplay.set(false);
Log.d(TAG, "数值变化:" + vm.isDisplay.get());
new Thread(new Runnable() {
@Override
public void run() {
try {
Thread.sleep(3000);
} catch (InterruptedException e) {
e.printStackTrace();
}
runOnUiThread(new Runnable() {
@Override
public void run() {
binding.philview.setVisibility(View.VISIBLE);
//View的变化结果，值将回写到ViewModel的isDisplay中
Log.d(TAG, "数值变化:" + vm.isDisplay.get());
}
});
}
}).start();
}
}代码运行结果日志输出：
08-28 15:13:15.303 11275-11275/zhangphil.test D/调试的MainActivity: 数值变化:false
08-28 15:13:15.335 11275-11275/zhangphil.test D/调试: setDisplayAttrChanged
08-28 15:13:15.335 11275-11275/zhangphil.test D/调试: getDisplay:0
08-28 15:13:15.335 11275-11275/zhangphil.test D/调试: setDisplay false
08-28 15:13:15.336 11275-11275/zhangphil.test D/调试: onVisibilityChanged
08-28 15:13:15.336 11275-11275/zhangphil.test D/调试: setDisplayAttrChanged -> onChange
08-28 15:13:15.336 11275-11275/zhangphil.test D/调试: getDisplay:4
08-28 15:13:18.310 11275-11275/zhangphil.test D/调试: onVisibilityChanged
08-28 15:13:18.311 11275-11275/zhangphil.test D/调试: setDisplayAttrChanged -> onChange
08-28 15:13:18.311 11275-11275/zhangphil.test D/调试: getDisplay:0
08-28 15:13:18.311 11275-11275/zhangphil.test D/调试的MainActivity: 数值变化:true
08-28 15:13:18.319 11275-11275/zhangphil.test D/调试: getDisplay:0
08-28 15:13:18.319 11275-11275/zhangphil.test D/调试: 重复设置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
