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我從SQLite數據庫填充文本和列表視圖。數據正確地從光標填充（我看到填充文本行的列表），但我無法看到行中的實際文本 - 我看到的只是空行。對於我的生活，我無法弄清楚我無法看到文本行中的數據。SQLite和填充列表視圖，android
我的佈局：
<?xml version="1.0" encoding="utf-8"?>
<TabHost xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@android:id/tabhost"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<LinearLayout
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:padding="5dp">
<TabWidget
android:id="@android:id/tabs"
android:layout_width="fill_parent"
android:layout_height="wrap_content" />
<FrameLayout
android:id="@android:id/tabcontent"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:padding="5dp" />
</LinearLayout>
</TabHost>
列表佈局：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="wrap_content">
</LinearLayout>
排佈局：
<?xml version="1.0" encoding="utf-8"?>
<TextView android:id="@+id/text1"
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="wrap_content"/>
我的主：
package com.gotquestions.gqapp;
import java.io.IOException;
import com.gotquestions.gqapp.DataBaseHelper;
import android.database.Cursor;
import android.app.TabActivity;
import android.content.Intent;
import android.content.res.Resources;
import android.database.SQLException;
import android.net.Uri;
import android.os.Bundle;
import android.widget.TabHost;
public class gqMain extends TabActivity {
/** Called when the activity is first created. */
private DataBaseHelper myDbHelper;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Resources res = getResources(); // Resource object to get Drawables
TabHost tabHost = getTabHost(); // The activity TabHost
TabHost.TabSpec spec; // Resusable TabSpec for each tab
Intent intent; // Reusable Intent for each tab
// Create an Intent to launch an Activity for the tab (to be reused)
intent = new Intent().setClass(this, TopicsActivity.class);
// Initialize a TabSpec for each tab and add it to the TabHost
spec = tabHost.newTabSpec("topics").setIndicator("" +
"Topics")
.setContent(intent);
tabHost.addTab(spec);
// Do the same for the other tabs
intent = new Intent().setClass(this, FavoritesActivity.class);
spec = tabHost.newTabSpec("favorites").setIndicator("Favorites")
.setContent(intent);
tabHost.addTab(spec);
// Do the same for the other tabs
intent = new Intent().setClass(this, AskActivity.class);
spec = tabHost.newTabSpec("ask").setIndicator("Ask")
.setContent(intent);
tabHost.addTab(spec);
// Do the same for the other tabs
intent = new Intent().setClass(this, BlogActivity.class);
spec = tabHost.newTabSpec("blog").setIndicator("Blog")
.setContent(intent);
tabHost.addTab(spec);
tabHost.setCurrentTab(0);
DataBaseHelper myDbHelper = new DataBaseHelper(this);
myDbHelper = new DataBaseHelper(this);
//test
try {
myDbHelper.createDataBase();
} catch (IOException ioe) {
throw new Error("Unable to create database");
}
try {
myDbHelper.openDataBase();
}catch(SQLException sqle){
throw sqle;
}
//Cursor c = myDbHelper.fetchAllTopics();
}
}
的TopicsActivity Tab..this內產生的數據我的主題活動就是在列表視圖中的數據顯示了，但我不能看到它。我查看了光標適配器，但沒有看到它。
package com.gotquestions.gqapp;
import com.gotquestions.gqapp.R.layout;
import android.R;
import android.app.ListActivity;
import android.database.Cursor;
import android.database.SQLException;
import android.os.Bundle;
import android.widget.SimpleCursorAdapter;
public class TopicsActivity extends ListActivity {
private DataBaseHelper myDbHelper;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//
DataBaseHelper myDbHelper = new DataBaseHelper(this);
myDbHelper = new DataBaseHelper(this);
//test
try {
myDbHelper.openDataBase();
}catch(SQLException sqle){
throw sqle;
}
setContentView(layout.list_layout);
Cursor c = myDbHelper.fetchAllTopics();
startManagingCursor(c);
String[] from = new String[] { DataBaseHelper.KEY_TITLE };
int[] to = new int[] { R.id.text1 };
// Now create an array adapter and set it to display using our row
SimpleCursorAdapter notes =
new SimpleCursorAdapter(this, layout.notes_row, c, from, to);
setListAdapter(notes);
myDbHelper.close();
}
}
我的數據庫幫手：
package com.gotquestions.gqapp;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
public class DataBaseHelper extends SQLiteOpenHelper{
//The Android's default system path of your application database.
private static String DB_PATH = "/data/data/com.gotquestions.gqapp/databases/";
private static String DB_NAME = "gotquestions_database.mp3";
public static final String KEY_TITLE = "topic_title";
public static final String KEY_ARTICLE_TITLE = "article_title";
public static final String KEY_ROWID = "_id";
private static final String TAG = null;
private SQLiteDatabase myDataBase;
//
private final Context myContext;
/**
* Constructor
* Takes and keeps a reference of the passed context in order to access to the application assets and resources.
* @param context
*/
public DataBaseHelper(Context context) {
super(context, DB_NAME, null, 1);
this.myContext = context;
}
/**
* Creates a empty database on the system and rewrites it with your own database.
* */
public void createDataBase() throws IOException{
boolean dbExist = checkDataBase();
if(dbExist){
//do nothing - database already exist
}else{
//By calling this method and empty database will be created into the default system path
//of your application so we are gonna be able to overwrite that database with our database.
this.getReadableDatabase();
try {
copyDataBase();
} catch (IOException e) {
throw new Error("Error copying database");
}
}
}
/**
* Check if the database already exist to avoid re-copying the file each time you open the application.
* @return true if it exists, false if it doesn't
*/
private boolean checkDataBase(){
SQLiteDatabase checkDB = null;
try{
String myPath = DB_PATH + DB_NAME;
checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
}catch(SQLiteException e){
//database does't exist yet.
}
if(checkDB != null){
checkDB.close();
}
return checkDB != null ? true : false;
}
/**
* Copies your database from your local assets-folder to the just created empty database in the
* system folder, from where it can be accessed and handled.
* This is done by transfering bytestream.
* */
private void copyDataBase() throws IOException{
//Open your local db as the input stream
InputStream myInput = myContext.getAssets().open(DB_NAME);
// Path to the just created empty db
String outFileName = DB_PATH + DB_NAME;
//Open the empty db as the output stream
OutputStream myOutput = new FileOutputStream(outFileName);
//transfer bytes from the inputfile to the outputfile
byte[] buffer = new byte[1024];
int length;
while ((length = myInput.read(buffer))>0){
myOutput.write(buffer, 0, length);
}
//Close the streams
myOutput.flush();
myOutput.close();
myInput.close();
}
public void openDataBase() throws SQLException{
//Open the database
String myPath = DB_PATH + DB_NAME;
myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
}
@Override
public synchronized void close() {
if(myDataBase != null)
myDataBase.close();
super.close();
}
@Override
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
}
@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 titles");
onCreate(db);
}
public Cursor getTitle(long rowId) throws SQLException
{
Cursor mCursor =
myDataBase.query(true, "topics", new String[] {
KEY_ROWID,
KEY_TITLE
},
KEY_ROWID + "=" + rowId,
null,
null,
null,
null,
null);
if (mCursor != null) {
mCursor.moveToFirst();
}
return mCursor;
}
public Cursor fetchAllTopics() {
return myDataBase.query("topics", new String[] {KEY_ROWID, KEY_TITLE},
null,
null,
null,
null,
null);
};
public Cursor fetchAllFavorites() {
return myDataBase.query("articles", new String[] {
KEY_ROWID,
KEY_ARTICLE_TITLE},
null,
null,
null,
null,
null);
};
}
謝謝，傑森。 ID：列表在那裏 - 我相信由於4空格縮進，stackoverflow編輯器將它留空了 這也許已經修復了它，但我相信我剛剛解決了它。我曾無意中導入了android.R，這一切都搞亂了。我刪除了這兩行，然後更正了佈局語句以包含R.並清除了它。 – 2010-06-06 07:08:14
@RobBushway瞭解使用哪個R以及爲什麼會有所不同:) – JoxTraex 2013-02-28 21:32:32