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12.4 DrySister看妹子应用(第一版)——4.添加数据缓存(加入SQLite) | 小熊教程

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1.一些BB

上节我们为DrySister编写了一个异步图片加载缓存框架——SisterLoader(妹子加载器) 成功的从网络加载的图片缓存到了磁盘和内存中,当我们断开网络后,仍然能够查看这些图片, 但是,细心的你可能发现了一个很尴尬的地方,我们在有网的情况下进入APP,获取到图片相关 的信息,比如URL,如果退出了,断网,然后进来,图片就加载不出来了,图片已经缓存了,但是 我们没有图片对应的URL,就显得有些鸡肋了。所以我们需要对后台接口返回的数据进行存储, 当每次加载的时候,把返回的数据信息存储到本地,然后当无网的时候,可以让他加载本地 数据!所以本节我们为DrySister添加SQLite用于存储相关数据。任务都说清楚了,搞起~


2.开始编写程序

在develop上开辟一个新的db分支,来完成本节相关代码的编写。

首先,我们添加一个用来判断网络状态的工具类:NetworkUtils.java, 就一个简单的判断网络是否可用的方法~这里我们还需要在AndroidManifest.xml 里加一个权限:android.permission.ACCESSNETWORKSTATE”的权限!

public class NetworkUtils {     /** 获取网络信息 */     private static NetworkInfo getActiveNetworkInfo(Context context) {         ConnectivityManager cm = (ConnectivityManager) context                 .getSystemService(Context.CONNECTIVITY_SERVICE);         return cm.getActiveNetworkInfo();     }          /** 判断网络是否可用 */     public static boolean isAvailable(Context context) {         NetworkInfo info = getActiveNetworkInfo(context);         return info != null && info.isAvailable();     } }

接着定义一个数据库字段常量的类:TableDefine.java, 在里面把数据库名,字段写上:

public class TableDefine {     public static final String TABLE_FULI = "fuli";     public static final String COLUMN_ID = "id";     public static final String COLUMN_FULI_ID = "_id";     public static final String COLUMN_FULI_CREATEAT = "createAt";     public static final String COLUMN_FULI_DESC = "desc";     public static final String COLUMN_FULI_PUBLISHEDAT = "publishedAt";     public static final String COLUMN_FULI_SOURCE = "source";     public static final String COLUMN_FULI_TYPE = "type";     public static final String COLUMN_FULI_URL = "url";     public static final String COLUMN_FULI_USED = "used";     public static final String COLUMN_FULI_WHO = "who"; }

再接着编写数据库的创建类:SisterOpenHelper.java,在里面完成数据库的创建

public class SisterOpenHelper extends SQLiteOpenHelper{      private static final String DB_NAME = "sister.db";  //数据库名     private static final int DB_VERSION = 1;    //数据库版本号      public SisterOpenHelper(Context context) {         super(context, DB_NAME, null, DB_VERSION);     }      @Override     public void onCreate(SQLiteDatabase db) {         String createTableSql = "CREATE TABLE IF NOT EXISTS " + TableDefine.TABLE_FULI + " ("                 + TableDefine.COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, "                 + TableDefine.COLUMN_FULI_ID + " TEXT, "                 + TableDefine.COLUMN_FULI_CREATEAT + " TEXT, "                 + TableDefine.COLUMN_FULI_DESC + " TEXT, "                 + TableDefine.COLUMN_FULI_PUBLISHEDAT + " TEXT, "                 + TableDefine.COLUMN_FULI_SOURCE + " TEXT, "                 + TableDefine.COLUMN_FULI_TYPE + " TEXT, "                 + TableDefine.COLUMN_FULI_URL + " TEXT, "                 + TableDefine.COLUMN_FULI_USED + " BOOLEAN, "                 + TableDefine.COLUMN_FULI_WHO + " TEXT"                 + ")";         db.execSQL(createTableSql);     }      @Override     public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { } }

再接着,我们需要编写一个数据库的操作类,就是做增删改查,分页查询等操作的类, 这里我们把这个类写成单例的:SisterDBHelper.java,里面的编写的方法有这些:

具体代码:

public class SisterDBHelper {      private static final String TAG = "SisterDBHelper";      private static SisterDBHelper dbHelper;     private SisterOpenHelper sqlHelper;     private SQLiteDatabase db;      private SisterDBHelper() {         sqlHelper = new SisterOpenHelper(DrySisterApp.getContext());     }      /** 单例 */     public static SisterDBHelper getInstance() {         if(dbHelper == null) {             synchronized (SisterDBHelper.class) {                 if(dbHelper == null) {                     dbHelper = new SisterDBHelper();                 }             }         }         return dbHelper;     }      /** 插入一个妹子 */     public void insertSister(Sister sister) {         db = getWritableDB();         ContentValues contentValues = new ContentValues();         contentValues.put(TableDefine.COLUMN_FULI_ID,sister.get_id());         contentValues.put(TableDefine.COLUMN_FULI_CREATEAT,sister.getCreateAt());         contentValues.put(TableDefine.COLUMN_FULI_DESC,sister.getDesc());         contentValues.put(TableDefine.COLUMN_FULI_PUBLISHEDAT,sister.getPublishedAt());         contentValues.put(TableDefine.COLUMN_FULI_SOURCE,sister.getSource());         contentValues.put(TableDefine.COLUMN_FULI_TYPE,sister.getType());         contentValues.put(TableDefine.COLUMN_FULI_URL,sister.getUrl());         contentValues.put(TableDefine.COLUMN_FULI_USED,sister.getUsed());         contentValues.put(TableDefine.COLUMN_FULI_WHO,sister.getWho());         db.insert(TableDefine.TABLE_FULI,null,contentValues);         closeIO(null);     }      /** 插入一堆妹子(使用事务) */     public void insertSisters(ArrayList<Sister> sisters) {         db = getWritableDB();         db.beginTransaction();         try{             for (Sister sister: sisters) {                 ContentValues contentValues = new ContentValues();                 contentValues.put(TableDefine.COLUMN_FULI_ID,sister.get_id());                 contentValues.put(TableDefine.COLUMN_FULI_CREATEAT,sister.getCreateAt());                 contentValues.put(TableDefine.COLUMN_FULI_DESC,sister.getDesc());                 contentValues.put(TableDefine.COLUMN_FULI_PUBLISHEDAT,sister.getPublishedAt());                 contentValues.put(TableDefine.COLUMN_FULI_SOURCE,sister.getSource());                 contentValues.put(TableDefine.COLUMN_FULI_TYPE,sister.getType());                 contentValues.put(TableDefine.COLUMN_FULI_URL,sister.getUrl());                 contentValues.put(TableDefine.COLUMN_FULI_USED,sister.getUsed());                 contentValues.put(TableDefine.COLUMN_FULI_WHO,sister.getWho());                 db.insert(TableDefine.TABLE_FULI,null,contentValues);             }             db.setTransactionSuccessful();         } finally {             if(db != null && db.isOpen()) {                 db.endTransaction();                 closeIO(null);             }         }     }      /** 删除妹子(根据_id) */     public void deleteSister(String _id) {         db = getWritableDB();         db.delete(TableDefine.TABLE_FULI,"_id =?",new String[]{_id});         closeIO(null);     }      /** 删除所有妹子 */     public void deleteAllSisters() {         db = getWritableDB();         db.delete(TableDefine.TABLE_FULI,null,null);         closeIO(null);     }      /** 更新妹子信息(根据_id) */     public void deleteSister(String _id,Sister sister) {         db = getWritableDB();         ContentValues contentValues = new ContentValues();         contentValues.put(TableDefine.COLUMN_FULI_ID,sister.get_id());         contentValues.put(TableDefine.COLUMN_FULI_CREATEAT,sister.getCreateAt());         contentValues.put(TableDefine.COLUMN_FULI_DESC,sister.getDesc());         contentValues.put(TableDefine.COLUMN_FULI_PUBLISHEDAT,sister.getPublishedAt());         contentValues.put(TableDefine.COLUMN_FULI_SOURCE,sister.getSource());         contentValues.put(TableDefine.COLUMN_FULI_TYPE,sister.getType());         contentValues.put(TableDefine.COLUMN_FULI_URL,sister.getUrl());         contentValues.put(TableDefine.COLUMN_FULI_USED,sister.getUsed());         contentValues.put(TableDefine.COLUMN_FULI_WHO,sister.getWho());         db.update(TableDefine.TABLE_FULI,contentValues,"_id =?",new String[]{_id});         closeIO(null);     }      /** 查询当前表中有多少个妹子 */     public int getSistersCount() {         db = getReadableDB();         Cursor cursor = db.rawQuery("SELECT COUNT (*) FROM " + TableDefine.TABLE_FULI,null);         cursor.moveToFirst();         int count = cursor.getInt(0);         Log.v(TAG,"count:" + count);         closeIO(cursor);         return count;     }      /** 分页查询妹子,参数为当前页和每一个的数量,页数从0开始算 */     public List<Sister> getSistersLimit(int curPage,int limit) {         db =  getReadableDB();         List<Sister> sisters = new ArrayList<>();         String startPos = String.valueOf(curPage * limit);  //数据开始位置         if(db != null) {             Cursor cursor = db.query(TableDefine.TABLE_FULI,new String[] {                     TableDefine.COLUMN_FULI_ID, TableDefine.COLUMN_FULI_CREATEAT,                     TableDefine.COLUMN_FULI_DESC, TableDefine.COLUMN_FULI_PUBLISHEDAT,                     TableDefine.COLUMN_FULI_SOURCE, TableDefine.COLUMN_FULI_TYPE,                     TableDefine.COLUMN_FULI_URL, TableDefine.COLUMN_FULI_USED,                     TableDefine.COLUMN_FULI_WHO,             },null,null,null,null,TableDefine.COLUMN_ID,startPos + "," + limit);             while (cursor.moveToNext()) {                 Sister sister = new Sister();                 sister.set_id(cursor.getString(cursor.getColumnIndex(TableDefine.COLUMN_FULI_ID)));                 sister.setCreateAt(cursor.getString(cursor.getColumnIndex(TableDefine.COLUMN_FULI_CREATEAT)));                 sister.setDesc(cursor.getString(cursor.getColumnIndex(TableDefine.COLUMN_FULI_DESC)));                 sister.setPublishedAt(cursor.getString(cursor.getColumnIndex(TableDefine.COLUMN_FULI_PUBLISHEDAT)));                 sister.setSource(cursor.getString(cursor.getColumnIndex(TableDefine.COLUMN_FULI_SOURCE)));                 sister.setType(cursor.getString(cursor.getColumnIndex(TableDefine.COLUMN_FULI_TYPE)));                 sister.setUrl(cursor.getString(cursor.getColumnIndex(TableDefine.COLUMN_FULI_URL)));                 sister.setUsed(cursor.getInt(cursor.getColumnIndex(TableDefine.COLUMN_FULI_USED)));                 sisters.add(sister);             }             closeIO(cursor);         }         return sisters;     }      /** 查询所有妹子 */     public List<Sister> getAllSisters() {         db = getReadableDB();         List<Sister> sisters = new ArrayList<>();         Cursor cursor = db.rawQuery("SELECT * FROM "+TableDefine.TABLE_FULI,null);         cursor.moveToFirst();         while (cursor.moveToNext()) {             Sister sister = new Sister();             sister.set_id(cursor.getString(cursor.getColumnIndex(TableDefine.COLUMN_FULI_ID)));             sister.setCreateAt(cursor.getString(cursor.getColumnIndex(TableDefine.COLUMN_FULI_CREATEAT)));             sister.setDesc(cursor.getString(cursor.getColumnIndex(TableDefine.COLUMN_FULI_DESC)));             sister.setPublishedAt(cursor.getString(cursor.getColumnIndex(TableDefine.COLUMN_FULI_PUBLISHEDAT)));             sister.setSource(cursor.getString(cursor.getColumnIndex(TableDefine.COLUMN_FULI_SOURCE)));             sister.setType(cursor.getString(cursor.getColumnIndex(TableDefine.COLUMN_FULI_TYPE)));             sister.setUrl(cursor.getString(cursor.getColumnIndex(TableDefine.COLUMN_FULI_URL)));             sister.setUsed(cursor.getInt(cursor.getColumnIndex(TableDefine.COLUMN_FULI_USED)));             sisters.add(sister);         }         closeIO(cursor);         return sisters;     }      /** 获得可写数据库的方法 */     private SQLiteDatabase getWritableDB() {         return sqlHelper.getWritableDatabase();     }      /** 获得可读数据库的方法 */     private SQLiteDatabase getReadableDB() {         return sqlHelper.getReadableDatabase();     }      /** 关闭cursor和数据库的方法 */     private void closeIO(Cursor cursor) {         if(cursor != null) {             cursor.close();         }         if(db != null) {             db.close();         }     }  }

嗯,还是蛮简单的,都是一些SQLite的方法调用而已,接着我们对布局做一下更改, 把activity_main.xml改成下面的代码,就是换成上一个和下一个这样:

<?xml version="1.0" encoding="utf-8"?> <RelativeLayout     xmlns:android="http://schemas.android.com/apk/res/android"     android:layout_width="match_parent"     android:layout_height="match_parent">      <Button         android:id="@+id/btn_previous"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:layout_alignParentBottom="true"         android:visibility="invisible"         android:text="上一个"/>      <Button         android:id="@+id/btn_next"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:layout_alignParentBottom="true"         android:layout_toRightOf="@id/btn_previous"         android:text="下一个"/>      <ImageView         android:id="@+id/img_show"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:layout_above="@+id/btn_previous"/>  </RelativeLayout>

最后就是对MainActivity.java的一些逻辑更改了,核心的要点如下:

  • 1.curPos和page的控制以及处理逻辑
  • 2.根据网络是否可用加载网络还是数据库数据
  • 3.加载网络数据时存储到数据库需要避免重复插入 等等。

代码实现:

public class MainActivity extends AppCompatActivity implements View.OnClickListener {     private Button previousBtn;     private Button nextBtn;     private ImageView showImg;      private ArrayList<Sister> data;     private int curPos = 0; //当前显示的是哪一张     private int page = 1;   //当前页数     private PictureLoader loader;     private SisterApi sisterApi;     private SisterTask sisterTask;     private SisterLoader mLoader;     private SisterDBHelper mDbHelper;      @Override     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.activity_main);         sisterApi = new SisterApi();         loader = new PictureLoader();         mLoader = SisterLoader.getInstance(MainActivity.this);         mDbHelper = SisterDBHelper.getInstance();         initData();         initUI();     }      private void initData() {         data = new ArrayList<>();         sisterTask = new SisterTask();         sisterTask.execute();     }      private void initUI() {         previousBtn = (Button) findViewById(R.id.btn_previous);         nextBtn = (Button) findViewById(R.id.btn_next);         showImg = (ImageView) findViewById(R.id.img_show);          previousBtn.setOnClickListener(this);         nextBtn.setOnClickListener(this);     }      @Override     public void onClick(View v) {         switch (v.getId()) {             case R.id.btn_previous:                 --curPos;                 if (curPos == 0) {                     previousBtn.setVisibility(View.INVISIBLE);                 }                 if (curPos == data.size() - 1) {                     sisterTask = new SisterTask();                     sisterTask.execute();                 } else if(curPos < data.size()) {                     mLoader.bindBitmap(data.get(curPos).getUrl(), showImg, 400, 400);                 }                 break;             case R.id.btn_next:                 previousBtn.setVisibility(View.VISIBLE);                 if(curPos < data.size()) {                     ++curPos;                 }                 if (curPos > data.size() - 1) {                     sisterTask = new SisterTask();                     sisterTask.execute();                 } else if(curPos < data.size()){                     mLoader.bindBitmap(data.get(curPos).getUrl(), showImg, 400, 400);                 }                 break;         }     }      private class SisterTask extends AsyncTask<Void, Void, ArrayList<Sister>> {          public SisterTask() {         }          @Override         protected ArrayList<Sister> doInBackground(Void... params) {             ArrayList<Sister> result = new ArrayList<>();             if (page < (curPos + 1) / 10 + 1) {                 ++page;             }             //判断是否有网络             if (NetworkUtils.isAvailable(getApplicationContext())) {                 result = sisterApi.fetchSister(10, page);                 //查询数据库里有多少个妹子,避免重复插入                 if(mDbHelper.getSistersCount() / 10 < page) {                     mDbHelper.insertSisters(result);                 }             } else {                 result.clear();                 result.addAll(mDbHelper.getSistersLimit(page - 1, 10));             }             return result;         }          @Override         protected void onPostExecute(ArrayList<Sister> sisters) {             super.onPostExecute(sisters);             data.addAll(sisters);             if (data.size() > 0 && curPos + 1 < data.size()) {                 mLoader.bindBitmap(data.get(curPos).getUrl(), showImg, 400, 400);             }         }          @Override         protected void onCancelled() {             super.onCancelled();             sisterTask = null;         }     }       @Override     protected void onDestroy() {         super.onDestroy();         if (sisterTask != null) {             sisterTask.cancel(true);         }     } }

3.运行效果图

操作步骤:

把项目跑起来后,一直按下一页下一页缓存一堆图片,接着断开网络,进入DrySister, Duang~,神奇的发现,有妹子出现了,按下一页或者上一页也可以切换图片,妈妈再也 不用担心我在没网的时候不可以看DrySister了!

运行截图:


4.小结

好的,本节在上节的基础上行添加了SQlite保存后台数据,当无网的时候也可以查看 妹子图片,代码的大的改动如上述,还有一些小改,具体看代码。 最后把db分支的代码合并到develop分支上,然后删除db分支,把更新后的 develop分支推送到Github!


代码下载:

https://github.com/coder-pig/DrySister/tree/develop 欢迎follow,star,觉得有什么想加进来的可以提下issues!

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