我正在开发一个使用SQLite的小应用程序。你能告诉我为什么在按下按钮视图和删除后应用程序崩溃？还有为什么ADD按钮没有创建新数据。
public class MainActivity extends AppCompatActivity {
DatabaseHelper myDB;
EditText editTextObsah, editTextNazev, editTextID;
Button buttonAdd, buttonView,buttonUpdate, buttonDelete;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
myDB = new DatabaseHelper(this);
editTextNazev = (EditText)findViewById(R.id.editTextObsah);
editTextObsah = (EditText)findViewById(R.id.editTextNazev);
editTextID = (EditText)findViewById(R.id.editTextID);
buttonAdd = (Button)findViewById(R.id.buttonAdd);
buttonView = (Button)findViewById(R.id.buttonView);
buttonUpdate = (Button)findViewById(R.id.buttonUpdate);
buttonDelete = (Button)findViewById(R.id.buttonDelete);
insertData();
viewAll();
updateData();
deleteData();
}
public void deleteData(){
buttonDelete.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Integer deletedRows = myDB.deleteData(editTextID.getText().toString());
if(deletedRows > 0)
Toast.makeText(MainActivity.this,"Data Deleted",Toast.LENGTH_LONG).show();
else
Toast.makeText(MainActivity.this,"Data not Deleted",Toast.LENGTH_LONG).show();
}
});
}
public void updateData(){
buttonUpdate.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
boolean isUpdated = myDB.updateData(editTextID.getText().toString(),editTextNazev.getText().toString(),editTextObsah.getText().toString());
if(isUpdated == true)
Toast.makeText(MainActivity.this,"Data Updated",Toast.LENGTH_LONG).show();
else
Toast.makeText(MainActivity.this,"Data not Updated",Toast.LENGTH_LONG).show();
}
});
}
public void insertData(){
buttonAdd.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
boolean isInserted = myDB.insertData(editTextNazev.getText().toString(),editTextObsah.getText().toString());
if(isInserted == true)
Toast.makeText(MainActivity.this,"Data Inserted",Toast.LENGTH_LONG).show();
else
Toast.makeText(MainActivity.this,"Data not Inserted",Toast.LENGTH_LONG).show();
}
});
}
public void viewAll() {
buttonView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Cursor res = myDB.getAllData();
if(res.getCount() == 0){
//show message
showMessage("Error","No data found");
return;
}
StringBuffer buffer = new StringBuffer();
while (res.moveToNext()) {
buffer.append("Id :"+ res.getString(0)+"\n");
buffer.append("Caption :"+ res.getString(1)+"\n");
buffer.append("Content :"+ res.getString(2)+"\n\n");
}
// Show all data
showMessage("Data",buffer.toString());
}
});
}
public void showMessage(String title, String Message) {
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setCancelable(true);
builder.setTitle(title);
builder.setMessage(Message);
builder.show();
}
}
我的数据库课程：
public class DatabaseHelper extends SQLiteOpenHelper {
public static final String DATABASE_NAME = "notes.db";
public static final String TABLE_NAME = "notes_table.db";
public static final String ID = "ID";
public static final String CAPTION = "CAPTION";
public static final String CONTENT = "CONTENT";
public DatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, 1);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("create table " + TABLE_NAME + " (ID INTEGER PRIMARY KEY AUTOINCREMENT,NAZEV TEXT,OBSAH TEXT)");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS "+TABLE_NAME);
onCreate(db);
}
public boolean insertData(String caption, String content){
SQLiteDatabase db = this.getWritableDatabase();
ContentValues CV = new ContentValues();
CV.put(CAPTION,caption);
CV.put(CONTENT,content);
long result = db.insert(TABLE_NAME,null,CV);
if(result == -1)
return false;
else
return true;
}
public Cursor getAllData() {
SQLiteDatabase db = this.getWritableDatabase();
Cursor res = db.rawQuery("select * from "+TABLE_NAME,null);
return res;
}
public boolean updateData(String id, String caption, String content){
try {
SQLiteDatabase db = this.getWritableDatabase();
ContentValues CV = new ContentValues();
CV.put(ID,id);
CV.put(CAPTION,caption);
CV.put(CONTENT,content);
db.update(TABLE_NAME, CV, "ID = ?",new String[]{ id });
}catch (Exception e) {
}
return true;
}
public Integer deleteData(String id) {
SQLiteDatabase db = this.getWritableDatabase();
return db.delete(TABLE_NAME,"ID = ?",new String[]{ id });
}}
错误记录
05-23 14:11:04.821 12666-12666/com.example.qwasyx0.semestralka E/SQLiteLog: (1) no such table: notes_table.db
05-23 14:11:04.821 12666-12666/com.example.qwasyx0.semestralka E/SQLiteDatabase: Error inserting CAPTION=Obsah CONTENT=Název
android.database.sqlite.SQLiteException: no such table: notes_table.db (code 1): , while compiling: INSERT INTO notes_table.db(CAPTION,CONTENT) VALUES (?,?)
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.SQLiteStatement.<init>(SQLiteStatement.java:31)
at android.database.sqlite.SQLiteDatabase.insertWithOnConflict(SQLiteDatabase.java:1472)
at android.database.sqlite.SQLiteDatabase.insert(SQLiteDatabase.java:1343)
at com.example.qwasyx0.semestralka.DatabaseHelper.insertData(DatabaseHelper.java:43)
at com.example.qwasyx0.semestralka.MainActivity$3.onClick(MainActivity.java:65)
at android.view.View.performClick(View.java:5637)
at android.view.View$PerformClick.run(View.java:22429)
at android.os.Handler.handleCallback(Handler.java:751)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
答案 0 :(得分：1)
更改您的创建查询，因为列名在create中是diff，而其他查询则是唯一的
#expander {
position:absolute;
width: 0;
height: 17px;
background-color: #FFF;
border-top: 1px solid red;
z-index: 999;
transform: translate(-50%, -50%);
top: 50%;
left: 50%;
-webkit-animation: expandline 2s;
}
@-webkit-keyframes expandline{
0% { width: 0%; }
50% { width: 50%; }
100% { width: 100%; }
}
以及表名
db.execSQL("create table " + TABLE_NAME + " (ID INTEGER PRIMARY KEY AUTOINCREMENT,"+CAPTION+" TEXT,"+CONTENT+" TEXT)");
还将数据库版本放在最终变量
中public static final String TABLE_NAME = "notes_table";
卸载现有应用，然后安装以检查效果，或者您也可以增加DBVERSION
答案 1 :(得分：0)
我猜测它与您的数据库版本有关。
在你的构造函数
中public DatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, 1);
}
你应该使用一个局部变量（例如DATABASE_VERSION），每当你对数据库结构进行更改时都需要增加它，这样就可以删除并重新创建表了。
所以使用这样的东西
// the database version
static final int DATABASE_VERSION = 2;
.....
public DatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, 1);
}