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Android-动态切换主题

发表于 分类于 阅读次数： Valine： 3.8k 3 分钟

前言

对于资讯阅读类app的来说，夜间模式是必不可少的。本文提供一种不重启Activity实现动态切换主题的方案。

思路分析

基于接口回调机制，每个基类(BaseActivity)都实现同一个接口 ThemeChangeCallback

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interface ThemeChangeCallback {
    void onChangeTheme();
}

用一个列表保存ThemeChangeCallback

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private static List<ThemeChangeCallback> sCallbacks = new ArrayList<ThemeChangeCallback>();

当改变主题时，对每个ThemeChangeCallback调用onChangeTheme，然后在BaseActivity的onChangeTheme方法中实现背景或者资源的切换即可.

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public static synchronized void changeTheme() {
    for (ThemeChangeCallback callback : sCallbacks)
        if (callback != null)
            callback.onChangeTheme();
}

实现

BaseActitivy.java

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public class BaseActivity extends AppCompatActivity implements ThemeUtils.ThemeChangeCallback {
    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        ThemeUtils.addCallback(this);
    }
    @Override
    protected void onDestroy() {
        super.onDestroy();
        ThemeUtils.removeCallback(this);
    }
    @Override
    public void onChangeTheme() {
        Drawable drawable = null;
        if (ThemeUtils.getCurrentThemeId() == ThemeUtils.DAY_THEME_ID) {
            drawable = getResources().getDrawable(R.color.colorPrimary);
        } else if (ThemeUtils.getCurrentThemeId() == ThemeUtils.NIGHT_THEME_ID) {
            drawable = getResources().getDrawable(R.color.colorAccent);
        }
        if (getWindow() != null) {
            getWindow().setBackgroundDrawable(drawable);
        }
        if (getSupportActionBar() != null) {
            getSupportActionBar().setBackgroundDrawable(drawable);
        }
    }
}

MainActivity.java

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public class MainActivity extends BaseActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button btn = (Button) findViewById(R.id.btn_change_bg);
        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                ThemeUtils.changeTheme();
            }
        });
    }
}

ThemeUtils.java

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public class ThemeUtils {
    private static List<ThemeChangeCallback> sCallbacks = new ArrayList<ThemeChangeCallback>();
    private static int sCurrentThemeId = 0 ;
    public static int DAY_THEME_ID = 0 ;
    public static int NIGHT_THEME_ID = 1 ;
    private ThemeUtils() {}
    public static void addCallback(ThemeChangeCallback callback) {
        if (callback != null) {
            sCallbacks.add(callback);
        }
    }
    public static void removeCallback(ThemeChangeCallback callback) {
        if (callback != null) {
            sCallbacks.remove(callback);
        }
    }
    public static synchronized void changeTheme() {
        sCurrentThemeId = sCurrentThemeId == DAY_THEME_ID ? NIGHT_THEME_ID : DAY_THEME_ID;
        for (ThemeChangeCallback callback : sCallbacks)
            if (callback != null)
                callback.onChangeTheme();
    }
    public static int getCurrentThemeId() {
        return sCurrentThemeId;
    }
    interface ThemeChangeCallback {
        void onChangeTheme();
    }
}

activity_main.xml

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<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.netease.changetheme.MainActivity">
    <Button
        android:id="@+id/btn_change_bg"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="change bg"
        android:layout_centerInParent="true"/>
</RelativeLayout>

效果

图1

缺陷

改变背景色时，沉浸式状态栏没有相应改变，有待优化。