Question

我知道您可以使用

限制查询

＆＃34; SELECT * FROM chargelog ORDER BY date DESC LIMIT 10＆＃34;

但问题是我不知道将它放在我的代码中的哪个位置。有人能帮我吗？一切正常，但列表视图永远不会结束。

DatabaseAdapter.java

public class DatabaseAdapter {
private static final int DBVER = 3;
private static final String COLUMN_ID = "_id";
private static final String COLUMN_DATE = "date";
private static final String COLUMN_PERCENT = "percent";
private static final String COLUMN_STATUS = "status";
private static final String DBNAME_CLOG = "chargelogs";
private static final String DBTABLE_CLOG = "chargelog";
private static final String DB_CREATE_TABLE_CLOG = "CREATE TABLE "
        + DBTABLE_CLOG + "(" + COLUMN_ID
        + " integer primary key autoincrement," + COLUMN_DATE
        + " text not null," + COLUMN_PERCENT + " text not null,"
        + COLUMN_STATUS + " text not null)";
private static final String DB_DROP_CLOG = "DROP TABLE IF EXISTS "
        + DBTABLE_CLOG;
private DBHelper mDbHelper;
private static SQLiteDatabase mDb;
private final Context mCtx;

public class DBHelper extends SQLiteOpenHelper {

    public DBHelper(Context context) {
        super(context, DBNAME_CLOG, null, DBVER);
    }

    @Override
    public void onCreate(SQLiteDatabase mDb) {
        mDb.execSQL(DB_CREATE_TABLE_CLOG);
    }

    @Override
    public void onUpgrade(SQLiteDatabase mDb, int oldVersion, int newVersion) {
        mDb.execSQL(DB_DROP_CLOG);
        onCreate(mDb);
    }

}

public DatabaseAdapter(Context ctx) {
    this.mCtx = ctx;
}

public DatabaseAdapter open() throws SQLException {
    mDbHelper = new DBHelper(mCtx);
    mDb = mDbHelper.getWritableDatabase();
    return this;
}

public void close() {
    mDbHelper.close();
}

public long createLog(String date, String percent, String status) {
    if (mDb == null)
        open();
    ContentValues initValues = new ContentValues();
    initValues.put(COLUMN_DATE, date);
    initValues.put(COLUMN_PERCENT, percent);
    initValues.put(COLUMN_STATUS, status);

    return mDb.insert(DBTABLE_CLOG, null, initValues);
}

public Cursor fetchInputs() {
    if (mDb == null)
        open();
    return mDb.query(DBTABLE_CLOG, new String[] { COLUMN_ID, COLUMN_DATE,
            COLUMN_PERCENT, COLUMN_STATUS }, null, null, null, null, null);
}

public ArrayList<Chargelog> getHistory() {
    ArrayList<Chargelog> ins = new ArrayList<Chargelog>();

    Cursor mCursor = fetchInputs();
    mCursor.moveToFirst();

    while (!mCursor.isAfterLast()) {
        Chargelog i = new Chargelog();
        i.setId(mCursor.getInt(0));
        i.setDate(mCursor.getString(1));
        i.setPercent(mCursor.getString(2));
        i.setStatus(mCursor.getString(3));
        ins.add(i);
        mCursor.moveToNext();
    }

    mCursor.close();
    return ins;
}
}

ChargeLogActivity.java

    @SuppressLint("SimpleDateFormat")
    public class ChargeLogActivity extends Activity {
/** Called when the activity is first created. */
private String strText;
private DatabaseAdapter mDb;
private boolean trun = true;
private Handler myHandler = new Handler();

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_chargelog);
    mDb = new DatabaseAdapter(this);
    mDb.open();

    startMonitor();
}

@Override
public void onDestroy() {
    trun = false;
    super.onDestroy();
}

private void startMonitor() {
    myThread.start();
}

private void updateNow() {
    TextView current = (TextView) findViewById(R.id.current);
    current.setText(strText);
    updateData();
}

private void batteryLevelUpdate() {

    BroadcastReceiver batteryLevelReceiver = new BroadcastReceiver() {
        public void onReceive(Context context, Intent intent) {
            int rawlevel =   intent.getIntExtra(BatteryManager.EXTRA_LEVEL,
                    -1);
            int scale = intent.getIntExtra(BatteryManager.EXTRA_SCALE, -1);
            int level = -1;
            if (rawlevel >= 0 && scale > 0) {
                level = (rawlevel * 100) / scale;
            }
            int status = intent
                    .getIntExtra(BatteryManager.EXTRA_STATUS, -1);

            String strStatus = "";
            switch (status) {

            case BatteryManager.BATTERY_STATUS_UNKNOWN:
                strStatus = "Unknown Charged";
                break;

            case BatteryManager.BATTERY_PLUGGED_USB:
                strStatus = "Starts Charging";
                mDb.createLog(DateFormat(cal.getTime()).toString(),
                        Integer.toString(level), strStatus);
                break;

            default:
                strStatus = "Not Charging";
                mDb.createLog(DateFormat(cal.getTime()).toString(),
                        Integer.toString(level), strStatus);
                break;

            case BatteryManager.BATTERY_STATUS_FULL:
                strStatus = "Fully Charged";
                mDb.createLog(DateFormat(cal.getTime()).toString(),
                        Integer.toString(level), strStatus);
                break;

            }
            strText = "\t\t\tDate\t" + "\t\t\tTime\t" + "\t\t\tLevel\t" + "\t\t\t\tStatus";

        }

    };

    // Register for the battery changed event
    IntentFilter batteryLevelFilter = new IntentFilter(
            Intent.ACTION_BATTERY_CHANGED);
    registerReceiver(batteryLevelReceiver, batteryLevelFilter);

}

private String DateFormat(Date time) {
    DateFormat dateFormat = new SimpleDateFormat("yyyy/MM/dd   HH:mm");
    // get current date time with Calendar()
    Calendar cal = Calendar.getInstance();
    return dateFormat.format(cal.getTime());
}

private void updateData() {
    final ArrayList<Chargelog> ins = mDb.getHistory();
    Chargelog i = new Chargelog();
    String date;
    String percent;
    String dstatus;
    ArrayList<HashMap<String, String>> data = new ArrayList<HashMap<String, String>>();
    for (int x = 0; x < ins.size(); x++) {
        i = ins.get(x);
        date = i.getDate();
        percent = i.getPercent();
        dstatus = i.getStatus();
        HashMap<String, String> datadata = new HashMap<String, String>(2);
        datadata.put("d", date);
        datadata.put("p", percent);
        datadata.put("s", dstatus);
        data.add(datadata);
    }
    ListView lv = (ListView) findViewById(R.id.lv1);
    CustListAdapter adp = new CustListAdapter(ChargeLogActivity.this, data,
            R.layout.cust_list_item, new String[] { "d", "p", "s" },
            new int[] { R.id.date, R.id.percent, R.id.status });

    lv.setAdapter(adp);
}

private Runnable myRun = new Runnable() {
    public void run() {
        updateNow();
    }
};

DateFormat dateFormat = new SimpleDateFormat("dd/mm/yyyy   HH:mm");
// get current date time with Calendar()
Calendar cal = Calendar.getInstance();

// using Thread to keep the process running
private Thread myThread = new Thread() {
    public void run() {
        do {
            batteryLevelUpdate();
            myHandler.post(myRun);
            try {
                Thread.sleep(10000);
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        } while (trun);
    }
};

}

Answer 1

我认为就在这里：

return mDb.query(DBTABLE_CLOG, new String[] { COLUMN_ID, COLUMN_DATE,
        COLUMN_PERCENT, COLUMN_STATUS }, null, null, null, null, null, "LIMIT 10");

但是没有测试，检查query的重载，我无法回想起确切的位置。

编辑，再添加一个null，认为就是它......

如何将listview限制为10

1 个答案: