我正在尝试使用预加载的数据库创建列表视图，该应用程序正在运行，但数据未显示。请帮助我。我使用数据库浏览器的Sqlite。或者有人可以举个例子吗？
这是我的DataListView.java
package com.example.thetrial;
import java.util.ArrayList;
import android.app.Activity;
import android.app.ListActivity;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.CursorAdapter;
import android.widget.ListView;
import android.widget.TextView;
public class DataListView extends Activity {
private DBHelper dbDBHelper = null;
private Cursor ourCursor = null;
private DBAdapter adapter = null;
@Override
public void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
try{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
ListView myListView = (ListView)findViewById(R.id.myListView);
dbDBHelper = new DBHelper(this);
dbDBHelper.createDataBase();
dbDBHelper.openDataBase();
ourCursor = dbDBHelper.getCursor();
startManagingCursor(ourCursor);
adapter = new DBAdapter(ourCursor);
myListView.setAdapter(adapter);
}catch (Exception e){
Log.e("Error", "Error in code: " + e.toString());
e.printStackTrace();
}
}
class DBAdapter extends CursorAdapter{
DBAdapter(Cursor c){
super(DataListView.this,c,0);
}
@Override
public void bindView(View view, Context context, Cursor cursor) {
// TODO Auto-generated method stub
DBHolder holder = (DBHolder)view.getTag();
holder.populateFrom(cursor, dbDBHelper);
}
@Override
public View newView(Context context, Cursor cursor, ViewGroup parent) {
// TODO Auto-generated method stub
LayoutInflater inflater = getLayoutInflater();
View view=inflater.inflate(R.layout.row, parent, false);
DBHolder holder = new DBHolder(view);
view.setTag(holder);
return(view);
}
}
static class DBHolder {
private TextView name = null;
DBHolder (View view){
name = (TextView)view.findViewById(R.id.text);
}
void populateFrom(Cursor c, DBHelper r){
name.setText(r.getName(c));
}
}
}
DBHelper.java
package com.example.thetrial;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Locale;
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.database.sqlite.SQLiteQueryBuilder;
public class DBHelper extends SQLiteOpenHelper{
public SQLiteDatabase DB;
private static String DB_Path = "/data/data/com.example.thetrial/databases/";
private static String DB_Name = "trialakoagain.db";
public static final String TABLE_Name = "linux_comm";
public static final String Column_Id = "_id";
public static final String Column_Comm = "comm";
public static final String Column_Desc = "desc";
private final Context myContext;
public DBHelper(Context context) {
super(context, DB_Name, null, 1);
this.myContext = context;
}
public void createDataBase(){
boolean dbExist = checkDataBase();
if(!dbExist){
this.getReadableDatabase();
copyDataBase();
}
}
/*
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");
}
}
}*/
private boolean checkDataBase() {
// TODO Auto-generated method stub
SQLiteDatabase checkDB = null;
try{
String myPath = DB_Path + DB_Name;
checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE);
checkDB.setLocale(Locale.getDefault());
//checkDB.setLockingEnabled(true);
checkDB.setVersion(1);
}catch(SQLiteException e){
//database does't exist yet.
}
if(checkDB != null){
checkDB.close();
}
return checkDB != null ? true : false;
}
private void copyDataBase() {
InputStream inputStream = null;
OutputStream outStream = null;
String outFileName = DB_Path + DB_Name;
try{
inputStream = myContext.getAssets().open(DB_Name);
outStream = new FileOutputStream(outFileName);
byte[] buffer = new byte[1024];
int length;
while ((length = inputStream.read(buffer)) > 0){
outStream.write(buffer,0,length);
}
outStream.flush();
outStream.close();
inputStream.close();
}catch (IOException e){
throw new Error("Problem copying db to resource!");
}
}
public void openDataBase() throws SQLException{
//Open the database
String myPath = DB_Path + DB_Name;
DB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE);
}
@Override
public synchronized void close() {
if(DB != null)
DB.close();
super.close();
}
@Override
public void onCreate(SQLiteDatabase db) {
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
// Add your public helper methods to access and get content from the database.
// You could return cursors by doing "return myDataBase.query(....)" so it'd be easy
// to you to create adapters for your views.
public Cursor getCursor(){
SQLiteQueryBuilder queryBuilder = new SQLiteQueryBuilder();
queryBuilder.setTables (TABLE_Name);
String [] asColumnToReturn = new String [] {Column_Id,Column_Comm,Column_Desc};
Cursor mCursor = queryBuilder.query(DB, asColumnToReturn, null, null, null, null, null);
return mCursor;
}
public String getName(Cursor c){
return(c.getString(2));
}
}
的Manifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.thetrial"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="14"
android:targetSdkVersion="21" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name=".DataListView"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
我不确定这些是否正确我只是看了一个教程，它从未说过main.xml和row.xml的需求
main.xml中
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<ListView
android:id="@+id/myListView"
android:layout_width="match_parent"
android:layout_height="wrap_content" >
</ListView>
row.xml
<?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" >
<TextView
android:id="@+id/text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
/>
答案 0 :(得分：1)
我认为问题出现是因为您忘记将数据库中的项目添加到适配器：
adapter = new DBAdapter(ourCursor);
myListView.setAdapter(adapter);
//add your adapter data here
adapter.notifyDataSetChanged(); //dont forget to refresh your list