Java 使用数据库进行搜索
我是初学者,我正在尝试开发简单的android应用程序,但我需要一些帮助。 我有一些按钮,标签等主要活动。按下一个按钮后,我启动第二个活动,Java 使用数据库进行搜索,java,android,Java,Android,我是初学者,我正在尝试开发简单的android应用程序,但我需要一些帮助。 我有一些按钮,标签等主要活动。按下一个按钮后,我启动第二个活动,SearchActivity,这里是我需要帮助的地方 SearchActivity.java public class SearchActivity extends AppCompatActivity { ListView lv; SearchView sv; ArrayAdapter<String&
SearchActivity
,这里是我需要帮助的地方
SearchActivity.java
public class SearchActivity extends AppCompatActivity {
ListView lv;
SearchView sv;
ArrayAdapter<String> adapter;
private ArrayList<String> items = getResults();
private ArrayList<String> getResults(){
DatabaseHelper db = new DatabaseHelper(this);
db.openDatabase();
ArrayList<String> resultList = new ArrayList<String>();
Cursor c = db.query(tablename,column names,null,null,null,null,null);
c.close();
db.close();
return resultList;
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_search);
lv = (ListView)findViewById(R.id.listview);
sv = (SearchView)findViewById(R.id.search);
adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1,items);
lv.setAdapter(adapter);
sv.setOnQueryTextListener(new SearchView.OnQueryTextListener() {
@Override
public boolean onQueryTextSubmit(String query) {
return false;
}
@Override
public boolean onQueryTextChange(String newText) {
adapter.getFilter().filter(newText);
return false;
}
});
}
}
public class DatabaseHelper extends SQLiteOpenHelper
{
String DB_PATH = null;
private static String DB_NAME = "dat";
private SQLiteDatabase myDatabase;
private final Context myContext;
public DatabaseHelper(Context context){
super(context, DB_NAME, null, 10);
this.myContext = context;
this.DB_PATH = "/data/data" + context.getPackageName() + "/" + "databases/";
Log.e("Path 1", DB_PATH);
}
public void createDatabase() throws IOException
{
boolean dbExist = checkDatabase();
if (dbExist) {
} else {
this.getReadableDatabase();
try {
copyDatabse();
} catch (IOException e){
throw new Error("Error copying database");
}
}
}
private boolean checkDatabase()
{
SQLiteDatabase checkDB = null;
try {
String myPath = DB_PATH + DB_NAME;
checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
} catch (SQLiteException e){
}
if(checkDB != null){
checkDB.close();
}
return checkDB != null ? true : false;
}
private void copyDatabse() throws IOException
{
InputStream myInput = myContext.getAssets().open(DB_NAME);
String outFileName = DB_PATH + DB_NAME;
OutputStream myOutput = new FileOutputStream(outFileName);
byte[] buffer = new byte[10];
int length;
while((length = myInput.read(buffer)) > 0){
myOutput.write(buffer, 0, length);
}
myOutput.flush();
myOutput.close();
myInput.close();
}
public void openDatabase() throws SQLiteException
{
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) {
if(newVersion > oldVersion){
try{
copyDatabse();
} catch (IOException e){
e.printStackTrace();
}
}
}
public Cursor query(String table, String[] columns, String selection, String[] selectionArgs, String groupBy, String having, String orderBy)
{
return myDatabase.query(table,columns,null,null,null,null,null);
}
}
而activity_search.xml只包含一个SearchView
和一个ListView
我在这里尝试的是从数据库中加载表数据,并能够使用SearchView
从中搜索,并在TextView
中显示结果,它只使用字符串数组,但这样一来,整个SearchActivity
会导致应用程序崩溃
以下是我的错误:
Caused by: android.database.sqlite.SQLiteException: no such table: Zastavky (code 1): , while compiling: SELECT Nazev FROM Zastavky
at android.database.sqlite.SQLiteConnection.nativePrepareStatement(Native Method)
at android.database.sqlite.SQLiteConnection.acquirePreparedStatement(SQLiteConnection.java:889)
at android.database.sqlite.SQLiteConnection.prepare(SQLiteConnection.java:500)
at android.database.sqlite.SQLiteSession.prepare(SQLiteSession.java:588)
at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:58)
at android.database.sqlite.SQLiteQuery.<init>(SQLiteQuery.java:37)
at android.database.sqlite.SQLiteDirectCursorDriver.query(SQLiteDirectCursorDriver.java:44)
at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1316)
at android.database.sqlite.SQLiteDatabase.rawQuery(SQLiteDatabase.java:1255)
at com.example.geote.ap1.SearchActivity.fetchData(SearchActivity.java:52)
at com.example.geote.ap1.SearchActivity.onCreate(SearchActivity.java:29)
at android.app.Activity.performCreate(Activity.java:5990)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
原因:android.database.sqlite.SQLiteException:没有这样的表:Zastavky(代码1):,编译时:从Zastavky中选择Nazev
位于android.database.sqlite.SQLiteConnection.nativePrepareStatement(本机方法)
位于android.database.sqlite.SQLiteConnection.acquirePreparedStatement(SQLiteConnection.java:889)
位于android.database.sqlite.SQLiteConnection.prepare(SQLiteConnection.java:500)
位于android.database.sqlite.SQLiteSession.prepare(SQLiteSession.java:588)
位于android.database.sqlite.SQLiteProgram.(SQLiteProgram.java:58)
位于android.database.sqlite.SQLiteQuery(SQLiteQuery.java:37)
位于android.database.sqlite.SQLiteDirectCursorDriver.query(SQLiteDirectCursorDriver.java:44)
位于android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1316)
位于android.database.sqlite.SQLiteDatabase.rawQuery(SQLiteDatabase.java:1255)
位于com.example.geote.ap1.SearchActivity.fetchData(SearchActivity.java:52)
位于com.example.geote.ap1.SearchActivity.onCreate(SearchActivity.java:29)
位于android.app.Activity.performCreate(Activity.java:5990)
位于android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
在android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
位于android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
在android.app.ActivityThread.access$800(ActivityThread.java:151)
在android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)上
位于android.os.Handler.dispatchMessage(Handler.java:102)
位于android.os.Looper.loop(Looper.java:135)
位于android.app.ActivityThread.main(ActivityThread.java:5254)
位于java.lang.reflect.Method.invoke(本机方法)
位于java.lang.reflect.Method.invoke(Method.java:372)
在com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)上
位于com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
感谢您的回复。您的课程在哪里?“整个SearchActivity导致应用程序失败”请准确解释“应用程序失败”时会发生什么。当我单击按钮启动SearchActivity时,我收到消息“应用程序已停止”。所以,整个应用程序都失败了。我的课在哪里?java在app>java和xml中,这是一个布局,所以在app>layout中。。当我问你的类在哪里时,我的意思是你发布的树代码都不在一个类中,所以它会给我编译器错误。请编辑代码以包含类。因此,我使用类进行编辑。我检查了代码,显然它无法从资产加载数据库,但我不知道为什么。我添加了我得到的错误。