android 在应用中切换语言

场景: 在设置中切换中英文,然后跳转MainActivity....
步骤:

1.在MyApplication 中初始化语言

public class MyApplication extends Application {
    private static MyApplication instance;
    public static MyApplication getInstance() {
        return instance;
    }
    public static MyApplication getContext() {
        return instance;
    }
    @Override
    public void onCreate() {
        super.onCreate();
        instance = this;
        String savedLanguage = LanguageUtil.getSavedLanguage();
        if (TextUtils.isEmpty(savedLanguage)) {
            LanguageUtil.setLanguage("cn"); // 设置默认语言为 "cn"
        } else {
            LanguageUtil.setLanguage(savedLanguage);
        }
    }
}

2.在  MainActivity 中 @Override onNewIntent()这个方法 , 如果不重写,当launch mode 为single task 时不会刷新

@Override
protected void onNewIntent(Intent intent) {
    if (intent.getAction() == "language changed") {
        finish();
        startActivity(new Intent(this, MainActivity.class));
    } else {
        super.onNewIntent(intent);
    }
}

3.设置界面代码和布局文件

public class SettingActivity extends BaseActivity {

    RadioGroup rgLanguage;
    RadioButton rbCn;
    RadioButton rbEn;
    private int checkedRadioButtonId;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_setting_language);

        rgLanguage = super.$(this, R.id.rgLanguage);
        rbCn = super.$(this, R.id.rbCn);
        rbEn = super.$(this, R.id.rbEn);

        if ("en".equals(LanguageUtil.getSavedLanguage())) {
            rbEn.setChecked(true);
        } else {
            rbCn.setChecked(true);
        }
        checkedRadioButtonId = rgLanguage.getCheckedRadioButtonId();

        super.$(this, R.id.btnConfirm).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (checkedRadioButtonId != rgLanguage.getCheckedRadioButtonId()) {
                    if (rbCn.isChecked()) {
                        LanguageUtil.setLanguage("cn");
                    } else if (rbEn.isChecked()) {
                        LanguageUtil.setLanguage("en");
                    }

                    finish();
                    Intent intent = new Intent(MyApplication.getContext(), FirstActivity.class);
                    intent.setAction("language changed");
                    startActivity(intent);
                } else {
                    finish();
                }
            }
        });
    }
}

////////////////////////////////////////////////////////////////////
public class BaseActivity extends Activity {
    public <T extends View> T $(Activity activity, int resId) {
        return (T) activity.findViewById(resId);
    }
}

设置界面  activity_setting_language.xml  布局

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

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:text="@string/switcher"/>

    <RadioGroup
        android:id="@+id/rgLanguage"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical">

        <RadioButton
            android:id="@+id/rbCn"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="中文"/>

        <RadioButton
            android:id="@+id/rbEn"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="English"/>
    </RadioGroup>

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

</LinearLayout>

4.LanguageUtil 代码

public class LanguageUtil {

    /**
     * 设置语言
     *
     * @param language "cn" = 中文, "en" = 英文
     */
    public static void setLanguage(String language) {
        Resources resources = MyApplication.getContext().getResources();
        Configuration configuration = resources.getConfiguration();
        configuration.locale = new Locale(language);
        resources.updateConfiguration(configuration, null);

        saveLanguage(language);
    }

    public static void saveLanguage(String language) {
        MyApplication.getContext().getSharedPreferences("settings", Context.MODE_PRIVATE)
                .edit().putString("language", language).commit();
    }

    public static String getSavedLanguage() {
        return MyApplication.getContext().getSharedPreferences("settings", Context.MODE_PRIVATE)
                .getString("language", "");
    }
}

5.AndroidManifest.xml 中添加权限,以及MyApplication的注册

    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>