使用Android BindingAdapter與InverseBindingAdapter實作SeekBar雙向（正向/反向）資料綁定

使用Android BindingAdapter與InverseBindingAdapter實作SeekBar雙向（正向/反向）資料綁定

在我之前寫的系列文章中，繼續深化Android資料綁定技術的使用。

結合常用的SeekBar，實作用Android DataBinding資料綁定技術，設定從資料模型的值修改SeekBar的進度，以及實作常見的SeekBar拖動時候的進度回寫到資料model中。也就是說，當使用者手動拖動SeekBar這一View時候，View産生的結果，回寫到我們建立的model中。

先任意建立一個資料模型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();
}
           

寫布局，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>           

關鍵的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) {
                //觸發反向資料的傳遞
                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("錯誤！", "InverseBindingListener為空!");
        } else {
            mInverseBindingListener = inverseBindingListener;
        }
    }
}           

測試的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);

        //設定一個初始值作為示範 資料 -> View
        //這是最常見的進度設定。
        progress.porgress.set(21);
    }
}           

代碼運作結果，初始化：

當手指拖動SeekBar時候，進度值回寫到Progress的progress中，也再TextView中得到反應：