Android右对齐实践及优化

回想起去年做过的一个维语音乐平台，要求实现双语版本，汉语和维语。在维语版本中要求文字、控件，右对齐显示，我们都知道大部分语言都是左对齐，android默认的对齐方式也是左对齐方式。而像维语和阿拉伯语这种语言都是右对齐的，即是从右往左读的。
  拿到这个问题我首先想到到的是自定义ViewGroup。233333~
  其实从Android 4.2 (api 17)开始 对rtl 提供了相应的支持。

项目中的实际效果

Paste_Image.png

那我们来试一下吧~

相关配置

1. minsdk 大于17
2. manifest 文件中添加 android:supportsRtl="true"
3. 使用
   android:layout_marginEnd=""
   android:layout_marginStart=""
   android:paddingEnd=""
   android:paddingStart=""

简单使用

• ViewGroup 设置 android:layoutDirection="rtl 或 trl";
• TextView 内文字对齐方式 android:textAlignmen = "textEnd 或 textStart" 或 android:textDirection="rtl 或 ltr"

特别的控件

imageview 右对齐

    <ImageView
     android:layout_width="wrap_content"
     android:layout_height="wrap_content"
     android:scaleX="-1" //反向
     android:src="@drawable/ic_record_voice_over_blue_900_36dp"
    />   

viewpager 与 tablayout 右对齐，要求至右往左滑动

    public class RTLViewPager extends ViewPager {
    
        // direction
        private boolean mIsRtlOriented;
        
        public RTLViewPager(Context context){
            this(context, null);
        }
        public RTLViewPager(Context context, AttributeSet attrs){
            super(context, attrs);
        }
    
        //rtl 时设置当前页码  自定义属性修改更好
        public void setRtlOriented(boolean isRtlOriented){
            mIsRtlOriented = isRtlOriented;
            if(mIsRtlOriented && getAdapter() != null){
                setCurrentItem(getAdapter().getCount() - 1 , false);
            }else{
                setCurrentItem(0 , false);
            }
        }
    }

设置 adapter 数据反置

public class CommonPagerAdapter extends FragmentStatePagerAdapter

{
    private final List<Fragment> mFragments = new ArrayList<>();
    private final List<String> mFragmentsTitles = new ArrayList<>();
    private boolean mIsRtrl;

    public CommonPagerAdapter(FragmentManager fm , boolean mIsRtrl)
    {
        super(fm);
        this.mIsRtrl = mIsRtrl;
    }

    public void addFragment(Fragment fragment , String title)
    {
        mFragments.add(fragment);
        mFragmentsTitles.add(title);
    }

    public void clearFragment()
    {
        mFragments.clear();
        mFragmentsTitles.clear();
    }

    @Override
    public Fragment getItem(int position)
    {
        if (mIsRtrl && mFragments.size() > 0)
        {
            return mFragments.get(mFragments.size() - position - 1);
        }
        else
        {
            return mFragments.get(position);
        }
    }

    @Override
    public int getCount()
    {
        return mFragments.size();
    }

    @Override
    public CharSequence getPageTitle(int position)
    {
        if (mIsRtrl && mFragmentsTitles.size() > 0)
        {
            return mFragmentsTitles.get(mFragmentsTitles.size() - position - 1);
        }
        else
        {
            return mFragmentsTitles.get(position);
        }
    }
}

完整布局代码

汉语布局 activity_main.xml

    <?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="#ffffff"
    android:orientation="horizontal">

    <android.support.design.widget.TabLayout
        android:id="@+id/act_tab"
        android:layout_width="wrap_content"
        android:layout_height="48dp"
        app:layout_scrollFlags="scroll"
        app:tabSelectedTextColor="#666666"
        app:tabTextColor="@android:color/darker_gray"
        app:tabIndicatorHeight="2dp"
        app:tabMode="scrollable"
        app:tabIndicatorColor="@color/colorPrimary">
    </android.support.design.widget.TabLayout>

</LinearLayout>

<com.yankang.rtldemo.RTLViewPager
    android:id="@+id/act_viewpager"
    android:layout_width="match_parent"
    android:layout_weight="1"
    android:layout_height="0dp">
</com.yankang.rtldemo.RTLViewPager>


<Button
    android:id="@+id/change_lang"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="@string/change_lang"/>

</LinearLayout>

维语布局 activity_main.xml

    <?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layoutDirection="rtl"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="#ffffff"
        android:orientation="horizontal">

        <android.support.design.widget.TabLayout
            android:id="@+id/act_tab"
            android:layout_width="wrap_content"
            android:layout_height="48dp"
            android:layoutDirection="ltr"
            app:layout_scrollFlags="scroll"
            app:tabSelectedTextColor="#666666"
            app:tabTextColor="@android:color/darker_gray"
            app:tabIndicatorHeight="2dp"
            app:tabMode="scrollable"
            app:tabIndicatorColor="@color/colorPrimary">
        </android.support.design.widget.TabLayout>

    </LinearLayout>

    <com.yankang.rtldemo.RTLViewPager
        android:id="@+id/act_viewpager"
        android:layout_width="match_parent"
        android:layout_weight="1"
        android:layout_height="0dp">
    </com.yankang.rtldemo.RTLViewPager>


    <Button
        android:id="@+id/change_lang"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/change_lang"/>

</LinearLayout>

文件夹结构（rtl布局我放在 layout_en_rUS 下）

Paste_Image.png

以上源码地址

---

好吧， 到这里我们基本实现了双语版本 ， 以及版本的切换。
但是 ，我们layout 多了一份 ， String.xml多了一份（这个无法避免），一方面需要同时维护两套布局，布局文件很多的情况下很不方便，另一方面也增大了app的大小。

布局优化

使用databinding 简化布局
App字符串常量类 StringVaule.java

package com.yankang.rtldemo.Strings;

import android.databinding.BaseObservable;
import android.databinding.Bindable;
import com.yankang.rtldemo.BR;

/**
 * Created by yankang on 2017/1/8.
 * app 字符串常量类
 */

public class StringVaule extends BaseObservable
{
     private boolean langType = false;
     @Bindable
     public boolean isLangType() {
          return langType;
     }

     public void setLangType(boolean langType)
     {
          this.langType = langType;
          notifyPropertyChanged(BR.langType);
     }

     // 文字
     public final String btn = "改变";
     public final String _btn = "change";
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android">
    <data>
        <import type="com.yankang.rtldemo.Strings.StringVaule"/>
        <import type="android.view.View"/>

        <variable
            name="string"
            type="StringVaule"/>
    </data>

    <LinearLayout
        xmlns:app="http://schemas.android.com/apk/res-auto"
        android:id="@+id/activity_main"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layoutDirection="@{string.langType ? View.LAYOUT_DIRECTION_RTL : View.LAYOUT_DIRECTION_LTR}"
        android:orientation="vertical">

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:background="#ffffff"
            android:orientation="horizontal">

            <android.support.design.widget.TabLayout
                android:id="@+id/act_tab"
                android:layout_width="wrap_content"
                android:layout_height="48dp"
                app:layout_scrollFlags="scroll"
                android:layoutDirection="ltr"
                app:tabSelectedTextColor="#666666"
                app:tabTextColor="@android:color/darker_gray"
                app:tabIndicatorHeight="2dp"
                app:tabMode="scrollable"
                app:tabIndicatorColor="@color/colorPrimary">
            </android.support.design.widget.TabLayout>

        </LinearLayout>

        <com.yankang.rtldemo.Widgets.RTLViewPager
            android:id="@+id/act_viewpager"
            android:layout_width="match_parent"
            android:layout_weight="1"
            android:layout_height="0dp">
        </com.yankang.rtldemo.Widgets.RTLViewPager>

        <Button
            android:id="@+id/change_lang"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@{string.langType ? string._btn : string.btn}"/>

    </LinearLayout>
</layout>

RecycleView item list_item.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="com.yankang.rtldemo.Strings.StringVaule"/>
        <import type="com.yankang.rtldemo.Model.Student"/>
        <variable
            name="string"
            type="StringVaule"/>
        <variable
            name="stu"
            type="Student"/>
    </data>

    <LinearLayout
        android:orientation="horizontal"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <ImageView
            android:layout_width="50dp"
            android:layout_height="50dp"
            android:layout_margin="15dp"
            android:scaleType="centerCrop"
                android:scaleX="@{string.langType ? -1f : 1f}"
            app:image="@{stu.imageUrl}"/>

        <LinearLayout
            android:layout_width="0dp"
            android:layout_weight="1"
            android:layout_gravity="center"
            android:orientation="vertical"
            android:layout_height="wrap_content">

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="@{stu.name}"/>

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginTop="10dp"
                android:text="@{stu.gender}"/>

        </LinearLayout>

        <ImageView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_vertical"
            android:layout_marginEnd="10dp"
            android:scaleX="@{string.langType ? -1f : 1f}"
            android:src="@drawable/ic_keyboard_arrow_right_black_36dp"/>

    </LinearLayout>

</layout>

MainActivity.java

package com.yankang.rtldemo1;

import android.content.Intent;
import android.databinding.DataBindingUtil;
import android.os.Bundle;
import android.support.design.widget.TabLayout;
import android.support.v4.app.Fragment;
import android.support.v7.app.AppCompatActivity;

import com.yankang.rtldemo1.Adapters.CommonPagerAdapter;
import com.yankang.rtldemo1.Widgets.RTLViewPager;
import com.yankang.rtldemo1.data.PreferManager;
import com.yankang.rtldemo1.databinding.ActivityMainBinding;

import butterknife.Bind;
import butterknife.ButterKnife;
import butterknife.OnClick;

import static com.yankang.rtldemo1.App.stringVaule;

public class MainActivity extends AppCompatActivity
{

@Bind(R.id.act_tab)
TabLayout actTab;
@Bind(R.id.act_viewpager)
RTLViewPager actViewpager;

private CommonPagerAdapter adapter;

private boolean isRtl = false;
private ActivityMainBinding binding;
private PreferManager preferManager;

@Override
protected void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    binding = DataBindingUtil.setContentView(this , R.layout.activity_main);
    ButterKnife.bind(this);
    initView();
}


private void initView()
{
    preferManager = PreferManager.getInstance(this);
    binding.setString(App.stringVaule);

    isRtl = preferManager.getLangType() == Constant.LANG_EN;
    stringVaule.setLangType(isRtl);

    adapter = new CommonPagerAdapter(getSupportFragmentManager() , isRtl);

    for (int i = 0 ; i < 3 ; i ++)
    {
        Fragment fragment = new TestFragment();
        adapter.addFragment(fragment , "标签" + i);
    }

    actTab.setupWithViewPager(actViewpager);
    actViewpager.setAdapter(adapter);
    actViewpager.setRtlOriented(isRtl);

}

@OnClick(R.id.change_lang)
public void change()
{
    if (preferManager.getLangType() == Constant.LANG_EN)
    {
        preferManager.setLangType(Constant.LANG_ZH);

    }else
    {
        preferManager.setLangType(Constant.LANG_EN);
    }

    startActivity(new Intent(this , MainActivity.class));
    finish();
}

}

RecycleView adapter 配置Databinding CommonAdapter.java

package com.yankang.rtldemo.Adapters;

import android.databinding.DataBindingUtil;
import android.databinding.ViewDataBinding;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import com.yankang.rtldemo.App;
import com.yankang.rtldemo.BR;
import com.yankang.rtldemo.Model.Student;
import com.yankang.rtldemo.R;

import java.util.ArrayList;


/**
 * Created by yankang on 2017/1/8.
 * MVVM 在recycleview 中的应用
 */

public class CommonAdapter extends RecyclerView.Adapter<CommonAdapter.ViewHoler>
{

    private final ArrayList<Student> mData = new ArrayList<>();

    public CommonAdapter(ArrayList<Student> data)
    {
        mData.addAll(data);
    }

    @Override
    public ViewHoler onCreateViewHolder(ViewGroup parent, int viewType)
    {
        ViewDataBinding binding = DataBindingUtil.inflate(LayoutInflater
                .from(parent.getContext()), R.layout.list_item, parent, false);
        ViewHoler holder = new ViewHoler(binding.getRoot());
        holder.setViewDataBinding(binding);
        return holder;
    }

    //设置数据
    @Override
    public void onBindViewHolder(ViewHoler holder, int position)
    {
        //修改绑定数据
        holder.getViewDataBinding().setVariable(BR.stu, mData.get(position));
        holder.getViewDataBinding().setVariable(BR.string , App.stringVaule);

        //刷新
        holder.getViewDataBinding().executePendingBindings();
    }

    @Override
    public int getItemCount() {
        return mData.size();
    }
    
    class ViewHoler extends RecyclerView.ViewHolder{

        private ViewDataBinding viewDataBinding;

        public ViewHoler(View itemView) {
            super(itemView);
        }

        public ViewDataBinding getViewDataBinding() {
            return viewDataBinding;
        }

        public void setViewDataBinding(ViewDataBinding viewDataBinding) {
            this.viewDataBinding = viewDataBinding;
        }
    }
}

以上源码地址

实际效果

Paste_Image.png

使用DataBinding后，我们不用再维护多套布局 ， 极大的简化了代码。总体来说还是很简单的。

end~