從Java中的SQLite值創建菜單

我想創建一個ListMenu使用來自SQLite數據庫的數據來定義每個MenuItem的名稱。因此，在一個名爲menu.java類我已經定義數組從Java中的SQLite值創建菜單

String classes [] = {};

應該保持每個菜單項名稱。

在DBAdapter類中，我創建了一個函數，以便用戶可以將信息插入到表中（這一切都可以正常工作）。

public long insertContact(String name, String code, String location, String comments, int days, int start, int end, String type) 
    { 
     ContentValues initialValues = new ContentValues(); 
     initialValues.put(KEY_NAME, name); 
     initialValues.put(KEY_CODE, code); 
     initialValues.put(KEY_LOCATION, location); 
     initialValues.put(KEY_COMMENTS, comments); 
     initialValues.put(KEY_DAYS, days); 
     initialValues.put(KEY_START, start); 
     initialValues.put(KEY_END, end); 
     initialValues.put(KEY_TYPE, type); 
     return db.insert(DATABASE_TABLE, null, initialValues); 
    }

這將是String s前插入到KEY_NAME，我需要填充該String陣列。有誰知道這是否可能？

非常感謝幫助傢伙。

如果我通過Sam/Mango實現該函數，那麼程序崩潰了，我是不是正確使用它，還是由於未知數組大小而導致的錯誤？

DBAdapter db = new DBAdapter(this); 
String classes [] = db.getClasses();

編輯：我要指出，如果我手動定義數組：

String classes [] = {"test1", "test2", "test3", etc};

它工作正常。錯誤是一個空指針異常

這裏是logcat（抱歉的格式）。我沒有用db = helper.getReadableDatabase（）來初始化;在getClasses（）函數中，但不幸的是它沒有解決問題。

11-11 22:53:39.117: D/dalvikvm(17856): Late-enabling CheckJNI 
11-11 22:53:39.297: D/TextLayoutCache(17856): Using debug level: 0 - Debug Enabled: 0 
11-11 22:53:39.337: D/libEGL(17856): loaded /system/lib/egl/libGLES_android.so 
11-11 22:53:39.337: D/libEGL(17856): loaded /system/lib/egl/libEGL_adreno200.so 
11-11 22:53:39.357: D/libEGL(17856): loaded /system/lib/egl/libGLESv1_CM_adreno200.so 
11-11 22:53:39.357: D/libEGL(17856): loaded /system/lib/egl/libGLESv2_adreno200.so 
11-11 22:53:39.387: I/Adreno200-EGLSUB(17856): <ConfigWindowMatch:2078>: Format RGBA_8888. 
11-11 22:53:39.407: D/memalloc(17856): /dev/pmem: Mapped buffer base:0x5c66d000 size:36593664 offset:32825344 fd:65 
11-11 22:53:39.417: E/(17856): Can't open file for reading 
11-11 22:53:39.417: E/(17856): Can't open file for reading 
11-11 22:53:39.417: D/OpenGLRenderer(17856): Enabling debug mode 0 
11-11 22:53:39.477: D/memalloc(17856): /dev/pmem: Mapped buffer base:0x5ecd3000 size:40361984 offset:36593664 fd:68 
11-11 22:53:40.507: D/memalloc(17856): /dev/pmem: Mapped buffer base:0x61451000 size:7254016 offset:3485696 fd:71 
11-11 22:53:41.077: I/Adreno200-EGLSUB(17856): <ConfigWindowMatch:2078>: Format RGBA_8888. 
11-11 22:53:41.077: D/memalloc(17856): /dev/pmem: Mapped buffer base:0x61c4c000 size:7725056 offset:7254016 fd:74 
11-11 22:53:41.097: D/memalloc(17856): /dev/pmem: Mapped buffer base:0x623aa000 size:8196096 offset:7725056 fd:80 
11-11 22:53:41.937: D/memalloc(17856): /dev/pmem: Mapped buffer base:0x62b7b000 size:8667136 offset:8196096 fd:83 
11-11 22:53:41.977: D/memalloc(17856): /dev/pmem: Unmapping buffer base:0x61c4c000 size:7725056 offset:7254016 
11-11 22:53:41.977: D/memalloc(17856): /dev/pmem: Unmapping buffer base:0x623aa000 size:8196096 offset:7725056 
11-11 22:53:41.977: D/memalloc(17856): /dev/pmem: Unmapping buffer base:0x62b7b000 size:8667136 offset:8196096 
11-11 22:53:42.167: I/Adreno200-EGLSUB(17856): <ConfigWindowMatch:2078>: Format RGBA_8888. 
11-11 22:53:42.177: D/memalloc(17856): /dev/pmem: Mapped buffer base:0x61c5d000 size:17084416 offset:13316096 fd:74 
11-11 22:53:42.317: D/memalloc(17856): /dev/pmem: Mapped buffer base:0x63853000 size:20852736 offset:17084416 fd:80 
11-11 22:53:42.357: D/OpenGLRenderer(17856): Flushing caches (mode 0) 
11-11 22:53:42.357: D/memalloc(17856): /dev/pmem: Unmapping buffer base:0x5c66d000 size:36593664 offset:32825344 
11-11 22:53:42.357: D/memalloc(17856): /dev/pmem: Unmapping buffer base:0x5ecd3000 size:40361984 offset:36593664 
11-11 22:53:42.367: D/memalloc(17856): /dev/pmem: Unmapping buffer base:0x61451000 size:7254016 offset:3485696 
11-11 22:53:42.757: D/memalloc(17856): /dev/pmem: Mapped buffer base:0x5c56d000 size:24621056 offset:20852736 fd:65 
11-11 22:53:44.247: D/AndroidRuntime(17856): Shutting down VM 
11-11 22:53:44.247: W/dalvikvm(17856): threadid=1: thread exiting with uncaught exception (group=0x40ac3210) 
11-11 22:53:44.257: E/AndroidRuntime(17856): FATAL EXCEPTION: main 
11-11 22:53:44.257: E/AndroidRuntime(17856): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{x.x.timetable/x.x.timetable.menu}: java.lang.NullPointerException 
11-11 22:53:44.257: E/AndroidRuntime(17856): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1891) 
11-11 22:53:44.257: E/AndroidRuntime(17856): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1992) 
11-11 22:53:44.257: E/AndroidRuntime(17856): at android.app.ActivityThread.access$600(ActivityThread.java:127) 
11-11 22:53:44.257: E/AndroidRuntime(17856): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1158) 
11-11 22:53:44.257: E/AndroidRuntime(17856): at android.os.Handler.dispatchMessage(Handler.java:99) 
11-11 22:53:44.257: E/AndroidRuntime(17856): at android.os.Looper.loop(Looper.java:137) 
11-11 22:53:44.257: E/AndroidRuntime(17856): at android.app.ActivityThread.main(ActivityThread.java:4441) 
11-11 22:53:44.257: E/AndroidRuntime(17856): at java.lang.reflect.Method.invokeNative(Native Method) 
11-11 22:53:44.257: E/AndroidRuntime(17856): at java.lang.reflect.Method.invoke(Method.java:511) 
11-11 22:53:44.257: E/AndroidRuntime(17856): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:823) 
11-11 22:53:44.257: E/AndroidRuntime(17856): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:590) 
11-11 22:53:44.257: E/AndroidRuntime(17856): at dalvik.system.NativeStart.main(Native Method) 
11-11 22:53:44.257: E/AndroidRuntime(17856): Caused by: java.lang.NullPointerException 
11-11 22:53:44.257: E/AndroidRuntime(17856): at android.content.ContextWrapper.openOrCreateDatabase(ContextWrapper.java:221) 
11-11 22:53:44.257: E/AndroidRuntime(17856): at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:157) 
11-11 22:53:44.257: E/AndroidRuntime(17856): at x.x.timetable.DBAdapter.getClasses(DBAdapter.java:151) 
11-11 22:53:44.257: E/AndroidRuntime(17856): at x.x.timetable.menu.<init>(menu.java:15) 
11-11 22:53:44.257: E/AndroidRuntime(17856): at java.lang.Class.newInstanceImpl(Native Method) 
11-11 22:53:44.257: E/AndroidRuntime(17856): at java.lang.Class.newInstance(Class.java:1319) 
11-11 22:53:44.257: E/AndroidRuntime(17856): at android.app.Instrumentation.newActivity(Instrumentation.java:1023) 
11-11 22:53:44.257: E/AndroidRuntime(17856): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1882) 
11-11 22:53:44.257: E/AndroidRuntime(17856): ... 11 more 
11-11 22:53:46.527: I/Process(17856): Sending signal. PID: 17856 SIG: 9 



package x.x.timetable; 

import android.content.ContentValues; 
import android.content.Context; 
import android.database.Cursor; 
import android.database.SQLException; 
import android.database.sqlite.SQLiteDatabase; 
import android.database.sqlite.SQLiteOpenHelper; 
import android.util.Log; 

public class DBAdapter { 
    static final String KEY_ROWID = "_id"; 
    static final String KEY_NAME = "name"; 
    static final String KEY_CODE = "code"; 
    static final String KEY_LOCATION = "location"; 
    static final String KEY_COMMENTS = "comments"; 
    static final String KEY_DAYS = "days"; 
    static final String KEY_START = "start"; 
    static final String KEY_END = "end"; 
    static final String KEY_TYPE = "type"; 


    static final String TAG = "DBAdapter"; 

    static final String DATABASE_NAME = "MyDB"; 
    static final String DATABASE_TABLE = "timetable"; 
    static final int DATABASE_VERSION = 2; 

    static final String DATABASE_CREATE = 
     "create table timetable (_id integer primary key autoincrement, " 
     + "name text not null, code text not null, location text not null, comments text not null, days INTEGER not null, start INTEGER not null, end INTEGER not null, type text not null);"; 

    final Context context; 

    DatabaseHelper DBHelper; 
    SQLiteDatabase db; 

    public DBAdapter(Context ctx) 
    { 
     this.context = ctx; 
     DBHelper = new DatabaseHelper(context); 
    } 

    private static class DatabaseHelper extends SQLiteOpenHelper 
    { 
     DatabaseHelper(Context context) 
     { 
      super(context, DATABASE_NAME, null, DATABASE_VERSION); 
     } 

     @Override 
     public void onCreate(SQLiteDatabase db) 
     { 
      try { 
       db.execSQL(DATABASE_CREATE); 
      } catch (SQLException e) { 
       e.printStackTrace(); 
      } 
     } 

     @Override 
     public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) 
     { 
      Log.w(TAG, "Upgrading database from version " + oldVersion + " to " 
        + newVersion + ", which will destroy all old data"); 
      db.execSQL("DROP TABLE IF EXISTS timetable"); 
      db.execSQL("DROP TABLE IF EXISTS contacts"); 
      onCreate(db); 
     } 
    } 

    //---opens the database--- 
    public DBAdapter open() throws SQLException 
    { 
     db = DBHelper.getWritableDatabase(); 
     return this; 
    } 

    //---closes the database--- 
    public void close() 
    { 
     DBHelper.close(); 
    } 

    public int count(){ 
     db = DBHelper.getWritableDatabase(); 
     String count = "SELECT count(*) FROM table"; 
     Cursor mcursor = db.rawQuery(count, null); 
     int icount = mcursor.getInt(0); 
     return icount; 
    } 

    //---insert a contact into the database--- 
    public long insertContact(String name, String code, String location, String comments, int days, int start, int end, String type) 
    { 
     ContentValues initialValues = new ContentValues(); 
     initialValues.put(KEY_NAME, name); 
     initialValues.put(KEY_CODE, code); 
     initialValues.put(KEY_LOCATION, location); 
     initialValues.put(KEY_COMMENTS, comments); 
     initialValues.put(KEY_DAYS, days); 
     initialValues.put(KEY_START, start); 
     initialValues.put(KEY_END, end); 
     initialValues.put(KEY_TYPE, type); 
     return db.insert(DATABASE_TABLE, null, initialValues); 
    } 

    //---deletes a particular contact--- 
    public boolean deleteContact(long rowId) 
    { 
     return db.delete(DATABASE_TABLE, KEY_ROWID + "=" + rowId, null) > 0; 
    } 

    //---retrieves all the Timetable--- 
    public Cursor getAllTimetable() 
    { 
     return db.query(DATABASE_TABLE, new String[] {KEY_ROWID, KEY_NAME, 
       KEY_CODE, KEY_LOCATION, KEY_COMMENTS, KEY_DAYS, KEY_START, KEY_END, KEY_TYPE}, null, null, null, null, null); 
    } 

    //---retrieves a particular contact--- 
    public Cursor getContact(long rowId) throws SQLException 
    { 
     Cursor mCursor = 
       db.query(true, DATABASE_TABLE, new String[] {KEY_ROWID, 
       KEY_NAME, KEY_CODE, KEY_LOCATION, KEY_COMMENTS, KEY_DAYS, KEY_START, KEY_END, KEY_TYPE}, KEY_ROWID + "=" + rowId, null, 
       null, null, null, null); 
     if (mCursor != null) { 
      mCursor.moveToFirst(); 
     } 
     return mCursor; 
    } 

    //---updates a contact--- 
    public boolean updateContact(long rowId, String name, String code, String location, String comments, int days, int start, int end, String type) 
    { 
     ContentValues args = new ContentValues(); 
     args.put(KEY_NAME, name); 
     args.put(KEY_CODE, code); 
     args.put(KEY_LOCATION, location); 
     args.put(KEY_COMMENTS, comments); 
     args.put(KEY_DAYS, days); 
     args.put(KEY_START, start); 
     args.put(KEY_END, end); 
     args.put(KEY_TYPE, type); 
     return db.update(DATABASE_TABLE, args, KEY_ROWID + "=" + rowId, null) > 0; 
    } 

    public String[] getClasses() { 

     db = DBHelper.getWritableDatabase(); 
     String[] columns = {KEY_NAME}; 
     Cursor c = db.query(DATABASE_TABLE, columns, null, null, null, null, null); 
     String[] classes = new String [c.getCount()]; 
     int i = 0; 
     while (c.moveToNext()) { 
      classes[i] = c.getString(0); 
      i++; 
     } 
     c.close(); 
     return classes; 
    } 
}

來源

2012-11-11 shanahobo86

按列表菜單，你想要一個選項菜單，ContextMenu，或ListView？ – Sam

任何人都可以幫忙嗎？迄今爲止的反饋非常感謝 – shanahobo86

我會幫你的，但我想回答我的問題。 :) – Sam

絕對有可能。你可以在數據庫類中創建一個返回字符串數組值的方法。

public String[] getClasses() { 
    String[] columns = {KEY_NAME}; 
    Cursor c = db.query(DATABASE_TABLE, columns, null, null, null, null, null); 
    String[] classes = new String [c.getCount()]; 
    int i = 0; 
    while (c.moveToNext()) { 
     classes[i] = c.getString(0); 
     i++; 
    } 
    c.close(); 
    return classes; 
}

來源

2012-11-11 21:06:15 mango

我希望你不介意，我更新了你的代碼，使用從遊標返回的行數而不是39。我也讓循環更快了幾毫秒，因爲我們不需要比較索引到類的大小，因爲'moveToNext（）'返回'true'，當有新的數據要讀取時 – Sam

'當然我不介意，它真的更優雅，只是生氣我沒有想到它自己 – mango

偉大的東西傢伙。已經在這很長一段時間，真的很感謝你的幫助！ – shanahobo86

您正在尋找

ArrayList<String> list= new ArrayList<String>(); 
list.add(name);

當你不知道的長度，或者您需要多少個元素在數據結構中添加，你不應該使用在許多情況下，陣列（不是全部）。改用ArrayList。擺脫列表的名稱做

list.get(ELEMENT_AT);

，如果你一定需要一個數組，第一填充列表，然後使用List.toArray();找回數組。

來源

2012-11-11 21:04:20 wtsang02

從我們在評論討論中，我假設你想要做這樣的事情在onCreate()：

public class menu extends ListActivity{ 
    DBAdapter db; 
    String[] classes; // = {"test", "test11", "test1", "test2", "test3",}; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     db = new DBAdapter(this); 
     db.open(); 
     classes = db.getClasses(); 
     setListAdapter(new ArrayAdapter<String>(menu.this, android.R.layout.simple_list_item_1, classes)); 
    }

這顯然使用了我幫芒果寫的方法。

來源

2012-11-11 22:44:25 Sam

從Java中的SQLite值創建菜單

回答

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