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OSChina App代码分析之BaseApplication

• 引:进入程序以后Application类是一个不的不进行分析的大类.在OSChina当中Application承当着保存配置数据的角色此外还提供显示提示的功能(Toast).当然他的子类AppContext扩张了更多的功能.这就是后话了.这一篇文章当中具体分析BaseApplication类

  首先抛出通过阅读BaseApplication类到底学到什么东西.

  1. sdk版本判断
  2. BaseApplication充当这个应用程序运行过程中的简单数据存储角色(通过sharedPreferences实现)
  3. 自定义Toast

BaseApplication.java

package net.oschina.app.base;import android.annotation.SuppressLint;import android.annotation.TargetApi;import android.app.Activity;import android.app.Application;import android.content.Context;import android.content.SharedPreferences;import android.content.SharedPreferences.Editor;import android.content.res.Resources;import android.os.Build;import android.util.DisplayMetrics;import android.view.Gravity;import android.view.LayoutInflater;import android.view.View;import android.widget.ImageView;import android.widget.TextView;import android.widget.Toast;import net.oschina.app.R;import net.oschina.app.util.StringUtils;@SuppressLint("InflateParams")public class BaseApplication extends Application {    //杂七杂八的数据都是存在在这个xml文件    private static String PREF_NAME = "creativelocker.pref";    //用来存储cache文件更新时间戳    private static String LAST_REFRESH_TIME = "last_refresh_time.pref";    static Context _context;    static Resources _resource;    //上一次Toast显示的文字    private static String lastToast = "";    //上一次Toast显示的时间    private static long lastToastTime;    //当前framework是否大于等于GINGERBREAD(Andrdoi 2.3)    //因为在GINGERBREAD以前的更新sharedPreferences只能    //调用commit函数,在GINGERBREAD及其以    //后的版本可以调用性能更好的apply函数    private static boolean sIsAtLeastGB;    //判断当前framework版本是否大于等于GINGERBREAD    //Build.VERSION.SDK_INIT已int形式保存当前framework版本号    //在Build.VERSION_CODES类里保存所知的版本号    static {        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.GINGERBREAD) {            sIsAtLeastGB = true;        }    }    @Override    public void onCreate() {        super.onCreate();        _context = getApplicationContext();        _resource = _context.getResources();    }    public static synchronized BaseApplication context() {        return (BaseApplication) _context;    }    public static Resources resources() {        return _resource;    }    /**     * 放入已读文章列表中     *     */    public static void putReadedPostList(String prefFileName, String key,                                         String value) {        SharedPreferences preferences = getPreferences(prefFileName);        int size = preferences.getAll().size();        Editor editor = preferences.edit();        //这里有一个bug?        //clear函数,只是把editor里面的list清空.并且会导致后在调用commit函数不会生效.        //具体        if (size >= 100) {            editor.clear();        }        editor.putString(key, value);        apply(editor);    }    /**     * 读取是否是已读的文章列表     *     * @return     */    public static boolean isOnReadedPostList(String prefFileName, String key) {        return getPreferences(prefFileName).contains(key);    }    /**     * 记录列表上次刷新时间     *     * @param key     * @param value     * @return void     * @author 火蚁     * 2015-2-9 下午2:21:37     */    public static void putToLastRefreshTime(String key, String value) {        SharedPreferences preferences = getPreferences(LAST_REFRESH_TIME);        Editor editor = preferences.edit();        editor.putString(key, value);        apply(editor);    }    /**     * 获取列表的上次刷新时间     *     * @param key     * @return     * @author 火蚁     * 2015-2-9 下午2:22:04     */    public static String getLastRefreshTime(String key) {        return getPreferences(LAST_REFRESH_TIME).getString(key, StringUtils.getCurTimeStr());    }    //GINGERBREAD以后的framework调用apply函数提交修改.之前的版本调用commit函数提交修改.    @TargetApi(Build.VERSION_CODES.GINGERBREAD)    public static void apply(SharedPreferences.Editor editor) {        if (sIsAtLeastGB) {            editor.apply();        } else {            editor.commit();        }    }    public static void set(String key, int value) {        Editor editor = getPreferences().edit();        editor.putInt(key, value);        apply(editor);    }    public static void set(String key, boolean value) {        Editor editor = getPreferences().edit();        editor.putBoolean(key, value);        apply(editor);    }    public static void set(String key, String value) {        Editor editor = getPreferences().edit();        editor.putString(key, value);        apply(editor);    }    public static boolean get(String key, boolean defValue) {        return getPreferences().getBoolean(key, defValue);    }    public static String get(String key, String defValue) {        return getPreferences().getString(key, defValue);    }    public static int get(String key, int defValue) {        return getPreferences().getInt(key, defValue);    }    public static long get(String key, long defValue) {        return getPreferences().getLong(key, defValue);    }    public static float get(String key, float defValue) {        return getPreferences().getFloat(key, defValue);    }    @TargetApi(Build.VERSION_CODES.HONEYCOMB)    public static SharedPreferences getPreferences() {        SharedPreferences pre = context().getSharedPreferences(PREF_NAME,                Context.MODE_MULTI_PROCESS);        return pre;    }    @TargetApi(Build.VERSION_CODES.HONEYCOMB)    public static SharedPreferences getPreferences(String prefName) {        return context().getSharedPreferences(prefName,                Context.MODE_MULTI_PROCESS);    }    public static int[] getDisplaySize() {        return new int[]{getPreferences().getInt("screen_width", 480),                getPreferences().getInt("screen_height", 854)};    }    //将屏幕规格信息存储起来    public static void saveDisplaySize(Activity activity) {        DisplayMetrics displaymetrics = new DisplayMetrics();        activity.getWindowManager().getDefaultDisplay()                .getMetrics(displaymetrics);        SharedPreferences.Editor editor = getPreferences().edit();        editor.putInt("screen_width", displaymetrics.widthPixels);        editor.putInt("screen_height", displaymetrics.heightPixels);        editor.putFloat("density", displaymetrics.density);        editor.commit();    }    public static String string(int id) {        return _resource.getString(id);    }    public static String string(int id, Object... args) {        return _resource.getString(id, args);    }    public static void showToast(int message) {        showToast(message, Toast.LENGTH_LONG, 0);    }    public static void showToast(String message) {        showToast(message, Toast.LENGTH_LONG, 0, Gravity.BOTTOM);    }    public static void showToast(int message, int icon) {        showToast(message, Toast.LENGTH_LONG, icon);    }    public static void showToast(String message, int icon) {        showToast(message, Toast.LENGTH_LONG, icon, Gravity.BOTTOM);    }    public static void showToastShort(int message) {        showToast(message, Toast.LENGTH_SHORT, 0);    }    public static void showToastShort(String message) {        showToast(message, Toast.LENGTH_SHORT, 0, Gravity.BOTTOM);    }    public static void showToastShort(int message, Object... args) {        showToast(message, Toast.LENGTH_SHORT, 0, Gravity.BOTTOM, args);    }    public static void showToast(int message, int duration, int icon) {        showToast(message, duration, icon, Gravity.BOTTOM);    }    public static void showToast(int message, int duration, int icon,                                 int gravity) {        showToast(context().getString(message), duration, icon, gravity);    }    public static void showToast(int message, int duration, int icon,                                 int gravity, Object... args) {        showToast(context().getString(message, args), duration, icon, gravity);    }    //上面一大寸showToast总归到要走到这里    public static void showToast(String message, int duration, int icon,                                 int gravity) {        //message为nul或者为"",就不好意思咯.一律居于门外        if (message != null && !message.equalsIgnoreCase("")) {            long time = System.currentTimeMillis();            //如果message显示的信息和上一回显示的是一样必须有2S的间隔            //如果message显示的信息和上一回显示的不一样那么立马请进            if (!message.equalsIgnoreCase(lastToast)                    || Math.abs(time - lastToastTime) > 2000) {                //根据layout文件生成View                //R.layout.view_toast就是一个相对布局里面,横着放着一个ImageView和TextView                //因为ImageView有时候会隐藏,TextView又是依赖ImageView布局的.                //所以TextView设置了layout_alignWithParentIfMissing属性                View view = LayoutInflater.from(context()).inflate(                        R.layout.view_toast, null);                ((TextView) //设置文字                view.findViewById(R.id.title_tv)).setText(message);                //还可设置图片哦                if (icon != 0) {                    ((ImageView) view.findViewById(R.id.icon_iv))                            .setImageResource(icon);                    ((ImageView) view.findViewById(R.id.icon_iv))                            .setVisibility(View.VISIBLE);                }                //创建Toast实例                Toast toast = new Toast(context());                //设置Toast实例的View                toast.setView(view);                //设置对其方式                if (gravity == Gravity.CENTER) {                    toast.setGravity(gravity, 0, 0);                } else {                    toast.setGravity(gravity, 0, 35);                }                //Toast显示时间                toast.setDuration(duration);                toast.show();                //记录显示的文字                lastToast = message;                //记录此次的现实时间戳                lastToastTime = System.currentTimeMillis();            }        }    }}

<?xml version="1.0" encoding="utf-8"?><FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="wrap_content"    android:layout_height="wrap_content"    android:background="@drawable/toast_background" >    <RelativeLayout        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:paddingBottom="@dimen/space_8"        android:paddingLeft="10.0dip"        android:paddingRight="10.0dip"        android:paddingTop="@dimen/space_8" >        <ImageView            android:id="@+id/icon_iv"            android:layout_width="wrap_content"            android:layout_height="40.0dip"            android:layout_centerVertical="true"            android:layout_marginRight="@dimen/space_8"            android:scaleType="fitCenter"            android:visibility="gone" />        <TextView            android:id="@+id/title_tv"            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:layout_alignWithParentIfMissing="true"            android:layout_toRightOf="@id/icon_iv"            android:gravity="center_vertical"            android:textColor="@color/white"            android:textSize="16.0dip" />    </RelativeLayout></FrameLayout>

总结:
1.SDK framework的判断通过两个关键类Build.VERSION和Build.VERSION_CODES.Build.VERSION记录着当前的版本是多少.Build.VERSION_CODES里面记录了所有版本号的信息

2.基于Application类的特殊性.因为在每个一Activity都可以访问到的相当一个单类?.Application在很多时候也充当保存配置的角色.

3.在使用Toast多数情况下都是调用Toast的静态方法makeText.事实上除了这方法.使用Toast提供构造函数的能更灵活使用Toast.灵活体现在能自定义Toast显示内部的View.还有就是可以设置Toast显示的位置.可以告诉妈妈Toast不用在呆在底部了!

附:
在api里面很清楚可以看到apply函数在GINGERBREAD才新加进的

参考:
1:SharedPreferences http://www.android-doc.com/reference/android/content/SharedPreferences.html

2:Editor http://www.android-doc.com/reference/android/content/SharedPreferences.Editor.html

3:Toast http://www.android-doc.com/reference/android/widget/Toast.html

4:Build.VERSION http://www.android-doc.com/reference/android/os/Build.VERSION.html

5:Build.VERSION_CODES http://www.android-doc.com/reference/android/os/Build.VERSION_CODES.html