使用Android BindingAdapter与InverseBindingAdapter实现SeekBar双向（正向/反向）数据绑定

在我之前写的系列文章中，继续深化Android数据绑定技术的使用。
结合常用的SeekBar，实现用Android DataBinding数据绑定技术，设置从数据模型的值修改SeekBar的进度，以及实现常见的SeekBar拖动时候的进度回写到数据model中。也就是说，当用户手动拖动SeekBar这一View时候，View产生的结果，回写到我们建立的model中。

先任意建立一个数据模型Progress.java：

package zhangphil.test;

import android.databinding.BaseObservable;
import android.databinding.ObservableInt;

/**
 * Created by Phil on 2017/9/4.
 */

public class Progress extends BaseObservable {
    public final ObservableInt porgress = new ObservableInt();
}

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>

        <variable
            name="progress"
            type="zhangphil.test.Progress" />
    </data>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <zhangphil.test.PhilSeekBar
            style="?android:attr/progressBarStyleHorizontal"
            android:layout_width="match_parent"
            android:layout_height="30dp"
            app:philprogress="@={progress.porgress}" />

        <TextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:gravity="center"
            android:text="@{String.valueOf(progress.porgress)}"
            android:textColor="@android:color/holo_blue_light"
            android:textSize="50dp" />

    </LinearLayout>
</layout>

关键的PhilSeekBar.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.widget.SeekBar;

/**
 * Created by Phil on 2017/9/4.
 */

public class PhilSeekBar extends SeekBar {
    private static InverseBindingListener mInverseBindingListener;

    public PhilSeekBar(Context context, AttributeSet attrs) {
        super(context, attrs);

        this.setOnSeekBarChangeListener(new OnSeekBarChangeListener() {

            @Override
            public void onProgressChanged(SeekBar seekBar, int i, boolean b) {
                //触发反向数据的传递
                if (mInverseBindingListener != null) {
                    mInverseBindingListener.onChange();
                }
            }

            @Override
            public void onStartTrackingTouch(SeekBar seekBar) {

            }

            @Override
            public void onStopTrackingTouch(SeekBar seekBar) {

            }
        });
    }

    @BindingAdapter(value = "philprogress", requireAll = false)
    public static void setPhilProgress(PhilSeekBar seekBar, int progress) {
        if (getPhilProgress(seekBar) != progress) {
            seekBar.setProgress(progress);
        }
    }

    @InverseBindingAdapter(attribute = "philprogress", event = "philprogressAttrChanged")
    public static int getPhilProgress(PhilSeekBar seekBar) {
        return seekBar.getProgress();
    }

    @BindingAdapter(value = {"philprogressAttrChanged"}, requireAll = false)
    public static void setPhilProgressAttrChanged(PhilSeekBar seekBar, InverseBindingListener inverseBindingListener) {
        if (inverseBindingListener == null) {
            Log.e("错误！", "InverseBindingListener为空!");
        } else {
            mInverseBindingListener = inverseBindingListener;
        }
    }
}

测试的MainActivity.java：

package zhangphil.test;

import android.app.Activity;
import android.databinding.DataBindingUtil;
import android.os.Bundle;

import zhangphil.test.databinding.ActivityMainBinding;

public class MainActivity extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        ActivityMainBinding binding = DataBindingUtil.setContentView(this, R.layout.activity_main);

        Progress progress = new Progress();
        binding.setProgress(progress);

        //设置一个初始值作为演示 数据 -> View
        //这是最常见的进度设置。
        progress.porgress.set(21);
    }
}

代码运行结果，初始化：

当手指拖动SeekBar时候，进度值回写到Progress的progress中，也再TextView中得到反应：