我正在制作应用程序。我的第一个活动显示了几个按钮。每个按钮都应该从数据库中的一个表中读取数据。我在 assets 文件夹中有数据库，并将 android 元数据和 _id 添加到数据库中。在我的主要活动中，我正在使用以下代码“导入”数据库：
public class DataBaseHelper extends SQLiteOpenHelper{
private static final String DB_PATH = "/data/data/com.mypackage/databases/";
private static final String DB_NAME = "dbname.sqlite";
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) {
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
上面的代码足够了吗？该数据库是否可用于其他活动？
从我现在的主要活动中，我想单击示例按钮“植物”。这应该将我重定向到下一个活动并创建一个列表视图，其中包含数据库植物表中的所有植物名称。
我正在使用以下代码进行重定向：
Button plantsBtn = (Button) findViewById(R.id.button5);
plantsBtn.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
// Intent myIntent = new Intent(view.getContext(), plantslist.class);
startActivityForResult(myIntent, 0);
}
});
这是我卡住的地方。我现在不知道如何只用名称填充列表视图。同样在单击列表视图中的植物名称后，我想转到另一个线性布局，该布局显示单击的特定植物的同一表中其他列的所有其他详细信息。
在数据库中，有许多表格，例如“汽车”，它们将遵循相同的原则，但我认为如果我能让它在一张桌子上工作，我就可以自己为其他桌子调整它。
我知道那里已经有很多教程，但我还没有真正找到一个让我理解或适应我的情况的教程。帮助将不胜感激！