如何在listview中显示数据库中的项目?

时间:2014-08-02 21:31:11

标签: android listview android-listview

我在这个论坛上看过很多关于这个问题的帖子,但无论我多累,我都能解决这个问题。我想将数据库中的项目显示到列表视图中。我厌倦了为listview.java编写代码,从数据库中查看项目,但它没有用。

DBAdapter.java

package protect.my.password;

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


// TO USE:
// Change the package (at top) to match your project.
// Search for "TODO", and make the appropriate changes.
public class DBAdapter {

    /////////////////////////////////////////////////////////////////////
    //  Constants & Data
    /////////////////////////////////////////////////////////////////////
    // For logging:
    private static final String TAG = "DBAdapter";

    // DB Fields
    public static final String KEY_ROWID = "_id";
    public static final int COL_ROWID = 0;
    /*
     * CHANGE 1:
     */
    // TODO: Setup your fields here:
    public static final String KEY_WEBSITE = "website";
    public static final String KEY_USERNAME = "username";
    public static final String KEY_PASSWORD = "password";

    // TODO: Setup your field numbers here (0 = KEY_ROWID, 1=...)
    public static final int COL_WEBSITE = 1;
    public static final int COL_USERNAME = 2;
    public static final int COL_PASSWORD = 3;


    public static final String[] ALL_KEYS = new String[] {KEY_ROWID, KEY_WEBSITE, KEY_USERNAME, KEY_PASSWORD};

    // DB info: it's name, and the table we are using (just one).
    public static final String DATABASE_NAME = "MyDb";
    public static final String DATABASE_TABLE = "mainTable";
    // Track DB version if a new version of your app changes the format.
    public static final int DATABASE_VERSION = 1;   

    private static final String DATABASE_CREATE_SQL = 
            "create table " + DATABASE_TABLE 
            + " (" + KEY_ROWID + " integer primary key autoincrement, "

            /*
             * CHANGE 2:
             */
            // TODO: Place your fields here!
            // + KEY_{...} + " {type} not null"
            //  - Key is the column name you created above.
            //  - {type} is one of: text, integer, real, blob
            //      (http://www.sqlite.org/datatype3.html)
            //  - "not null" means it is a required field (must be given a value).
            // NOTE: All must be comma separated (end of line!) Last one must have NO comma!!
            + KEY_WEBSITE + " text not null, "
            + KEY_USERNAME + " text not null, "
            + KEY_PASSWORD + " string not null"

            // Rest  of creation:
            + ");";

    // Context of application who uses us.
    private final Context context;

    private DatabaseHelper myDBHelper;
    private SQLiteDatabase db;

    /////////////////////////////////////////////////////////////////////
    //  Public methods:
    /////////////////////////////////////////////////////////////////////

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

    // Open the database connection.
    public DBAdapter open() {
        db = myDBHelper.getWritableDatabase();
        return this;
    }

    // Close the database connection.
    public void close() {
        myDBHelper.close();
    }

    // Add a new set of values to the database.
    public long insertRow(String website, String username, String password) {
        /*
         * CHANGE 3:
         */     
        // TODO: Update data in the row with new fields.
        // TODO: Also change the function's arguments to be what you need!
        // Create row's data:
        ContentValues initialValues = new ContentValues();
        initialValues.put(KEY_WEBSITE, website);
        initialValues.put(KEY_USERNAME, username);
        initialValues.put(KEY_PASSWORD, password);

        // Insert it into the database.
        return db.insert(DATABASE_TABLE, null, initialValues);
    }

    // Delete a row from the database, by rowId (primary key)
    public boolean deleteRow(long rowId) {
        String where = KEY_ROWID + "=" + rowId;
        return db.delete(DATABASE_TABLE, where, null) != 0;
    }

    public void deleteAll() {
        Cursor c = getAllRows();
        long rowId = c.getColumnIndexOrThrow(KEY_ROWID);
        if (c.moveToFirst()) {
            do {
                deleteRow(c.getLong((int) rowId));              
            } while (c.moveToNext());
        }
        c.close();
    }

    // Return all data in the database.
    public Cursor getAllRows() {
        String where = null;
        Cursor c =  db.query(true, DATABASE_TABLE, ALL_KEYS, 
                            where, null, null, null, null, null);
        if (c != null) {
            c.moveToFirst();
        }
        return c;
    }

    // Get a specific row (by rowId)
    public Cursor getRow(long rowId) {
        String where = KEY_ROWID + "=" + rowId;
        Cursor c =  db.query(true, DATABASE_TABLE, ALL_KEYS, 
                        where, null, null, null, null, null);
        if (c != null) {
            c.moveToFirst();
        }
        return c;
    }

    // Change an existing row to be equal to new data.
    public boolean updateRow(long rowId, String webSite, String userName, String passWord) {
        String where = KEY_ROWID + "=" + rowId;

        /*
         * CHANGE 4:
         */
        // TODO: Update data in the row with new fields.
        // TODO: Also change the function's arguments to be what you need!
        // Create row's data:
        ContentValues newValues = new ContentValues();
        newValues.put(KEY_WEBSITE, webSite);
        newValues.put(KEY_USERNAME, userName);
        newValues.put(KEY_PASSWORD, passWord);

        // Insert it into the database.
        return db.update(DATABASE_TABLE, newValues, where, null) != 0;
    }



    /////////////////////////////////////////////////////////////////////
    //  Private Helper Classes:
    /////////////////////////////////////////////////////////////////////

    /**
     * Private class which handles database creation and upgrading.
     * Used to handle low-level database access.
     */
    private static class DatabaseHelper extends SQLiteOpenHelper
    {
        DatabaseHelper(Context context) {
            super(context, DATABASE_NAME, null, DATABASE_VERSION);
        }

        @Override
        public void onCreate(SQLiteDatabase _db) {
            _db.execSQL(DATABASE_CREATE_SQL);           
        }

        @Override
        public void onUpgrade(SQLiteDatabase _db, int oldVersion, int newVersion) {
            Log.w(TAG, "Upgrading application's database from version " + oldVersion
                    + " to " + newVersion + ", which will destroy all old data!");

            // Destroy old database:
            _db.execSQL("DROP TABLE IF EXISTS " + DATABASE_TABLE);

            // Recreate new database:
            onCreate(_db);
        }
    }
}

Listview.java

package protect.my.password;


import java.util.List;

import android.app.Activity;
import android.database.Cursor;
import android.os.Bundle;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.TextView;

public class Listview extends Activity {
    ListView listview;
    TextView empty;
    String selected;
    List<String> list;
    String[] filenames;

    DBAdapter myDb;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        listview = (ListView) findViewById(R.id.dblist);
        openDB();
        listviewitems();
        myDb.close();
    }

    private void listviewitems() {
        // TODO Auto-generated method stub

        Cursor cursor = myDb.getAllRows();

        // populate the message from the cursor

        // Reset cursor to start, checking to see if there's data:

                // Process the data:
                if (cursor.moveToFirst()) {
        do {
                String website = cursor.getString(DBAdapter.COL_WEBSITE);
                String username = cursor.getString(DBAdapter.COL_USERNAME);
                String password = cursor.getString(DBAdapter.COL_PASSWORD);

                String[] values = new String[] { website, username, password };
                ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
                        R.layout.main, R.id.dblist, values);
                    listview.setAdapter(adapter);
        // Close the cursor to avoid a resource leak.
        cursor.close();
} while(cursor.moveToNext());

    }

    }

    private void openDB() {
        myDb = new DBAdapter(this);
        myDb.open();
    }

}

main.xml中

<?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" >


     <ListView
        android:id="@+id/dblist"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >
    </ListView>

</LinearLayout>

可能代码看起来很有趣,我不是专业但初学者。欢迎任何帮助。任何人都可以告诉我这是什么错误,或者我的代码对于Listview.java都是愚蠢的,需要重新开始。

更新1:根据我在下面得到的答案编辑代码后,它就可以了。但我有另一个问题。如果只有数据库有一些项目,那么只有应用程序可以工作,但如果数据库为空,那么应用程序崩溃。任何帮助我该如何解决?下面是我的日志猫。

08-02 19:36:36.026: W/dalvikvm(3825): threadid=1: thread exiting with uncaught exception (group=0xb4a71ba8)
08-02 19:36:36.086: E/AndroidRuntime(3825): FATAL EXCEPTION: main
08-02 19:36:36.086: E/AndroidRuntime(3825): Process: protect.my.password, PID: 3825
08-02 19:36:36.086: E/AndroidRuntime(3825): java.lang.RuntimeException: Unable to start activity ComponentInfo{protect.my.password/protect.my.password.Listview}: android.database.CursorIndexOutOfBoundsException: Index 0 requested, with a size of 0
08-02 19:36:36.086: E/AndroidRuntime(3825):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
08-02 19:36:36.086: E/AndroidRuntime(3825):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
08-02 19:36:36.086: E/AndroidRuntime(3825):     at android.app.ActivityThread.access$800(ActivityThread.java:135)
08-02 19:36:36.086: E/AndroidRuntime(3825):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
08-02 19:36:36.086: E/AndroidRuntime(3825):     at android.os.Handler.dispatchMessage(Handler.java:102)
08-02 19:36:36.086: E/AndroidRuntime(3825):     at android.os.Looper.loop(Looper.java:136)
08-02 19:36:36.086: E/AndroidRuntime(3825):     at android.app.ActivityThread.main(ActivityThread.java:5017)
08-02 19:36:36.086: E/AndroidRuntime(3825):     at java.lang.reflect.Method.invokeNative(Native Method)
08-02 19:36:36.086: E/AndroidRuntime(3825):     at java.lang.reflect.Method.invoke(Method.java:515)
08-02 19:36:36.086: E/AndroidRuntime(3825):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
08-02 19:36:36.086: E/AndroidRuntime(3825):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
08-02 19:36:36.086: E/AndroidRuntime(3825):     at dalvik.system.NativeStart.main(Native Method)
08-02 19:36:36.086: E/AndroidRuntime(3825): Caused by: android.database.CursorIndexOutOfBoundsException: Index 0 requested, with a size of 0
08-02 19:36:36.086: E/AndroidRuntime(3825):     at android.database.AbstractCursor.checkPosition(AbstractCursor.java:426)
08-02 19:36:36.086: E/AndroidRuntime(3825):     at android.database.AbstractWindowedCursor.checkPosition(AbstractWindowedCursor.java:136)
08-02 19:36:36.086: E/AndroidRuntime(3825):     at android.database.AbstractWindowedCursor.getString(AbstractWindowedCursor.java:50)
08-02 19:36:36.086: E/AndroidRuntime(3825):     at protect.my.password.Listview.listviewitems(Listview.java:54)
08-02 19:36:36.086: E/AndroidRuntime(3825):     at protect.my.password.Listview.onCreate(Listview.java:36)
08-02 19:36:36.086: E/AndroidRuntime(3825):     at android.app.Activity.performCreate(Activity.java:5231)
08-02 19:36:36.086: E/AndroidRuntime(3825):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
08-02 19:36:36.086: E/AndroidRuntime(3825):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)

更新2: 得到了错误的答案。我不得不使用:

if(cursor != null && cursor.moveToFirst()){
   // my codes
}
    cursor.close();

2 个答案:

答案 0 :(得分:1)

首先,您应该通知您的适配器,ListView有其他内容,您可以使用

yourAdapter.notifyDataSetChanged();
listView.setAdapter(yourAdapter);

其次,您应该在另一个ListViewThread中执行AsyncTask的人口统计,以便数据库操作时间过长,如果您不这样做这样,在您调用ListView填充方法后,您的数据库内容就会可用,并且您将始终为空ListView但内容来自数据库。

答案 1 :(得分:0)

这是错的!

ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
                        R.layout.main, R.id.dblist, values);

应替换为

ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
                        /* your row layout not your main activity layout */,
                        /* ID of a TextView for printing on it */, values);

或者尝试Android的简单ListView项目:

ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
                        android.R.layout.simple_list_item_1, values);

更新#1

List<String> values = new ArrayList<String>();

do {
    String website = cursor.getString(DBAdapter.COL_WEBSITE);
    String username = cursor.getString(DBAdapter.COL_USERNAME);
    String password = cursor.getString(DBAdapter.COL_PASSWORD);

    values.add(website + " - " + username + " - " + password);
} while(cursor.moveToNext());

ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
                                  R.layout.main, R.id.dblist, values);
listview.setAdapter(adapter);

 // Close the cursor to avoid a resource leak.
cursor.close();