我正在构建一个应用程序，用户通过Java代码动态生成学期（按钮）。让我们说用户生成大约4个按钮（用户最多可以生成8个），我想将其存储到我创建的SQLite数据库中。这是我的第一个应用程序，可能是我第一次使用SQLite数据库。我浏览了SQLite Android教程，但我的应用程序与他们使用的示例相比有点不同。
我需要帮助的是，能够将动态生成的按钮存储到我的数据库中，以便下次再次启动应用程序时保存完全相同的数量。我还需要使用onUpgrade连接delete（menuItem和alertdialog）函数。
这是我的Mainactivity.java。这是我生成所有UI的地方。它也是我的主页。
public class MainActivity extends AppCompatActivity {
int counter = 0;
FloatingActionButton addingSemester;
Button semesterButton;
LinearLayout semesterLayout;
GridLayout semesterGridLayout;
LinearLayout.LayoutParams portraitLayoutParams = new LinearLayout.LayoutParams(
AppBarLayout.LayoutParams.MATCH_PARENT,
AppBarLayout.LayoutParams.WRAP_CONTENT);
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
addingSemester = (FloatingActionButton) findViewById(R.id.addActionButton);
semesterLayout = (LinearLayout) findViewById(R.id.main_layout);
semesterGridLayout = (GridLayout) findViewById(R.id.semester_grid_layout);
semesterButton = new Button(MainActivity.this);
if (savedInstanceState != null) {
counter = savedInstanceState.getInt("counter");
for (int i = 0; i < counter; i++) {
addSemesterButton(i);
}
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater menuInflater = getMenuInflater();
menuInflater.inflate(R.menu.main, menu);
return super.onCreateOptionsMenu(menu);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
if (id == R.id.delete) {
new AlertDialog.Builder(MainActivity.this)
.setTitle("Delete entry")
.setMessage("Are you sure you want to delete everything?")
.setCancelable(true)
.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
if (MainActivity.this.getResources().getBoolean(R.bool.is_landscape)) {
if (semesterGridLayout.getChildCount() > 0) {
semesterGridLayout.removeAllViews();
} else {
Toast.makeText(MainActivity.this, "There is nothing to delete", Toast.LENGTH_SHORT).show();
}
} else if (!MainActivity.this.getResources().getBoolean(R.bool.is_landscape)) {
if (semesterLayout.getChildCount() > 0) {
semesterLayout.removeAllViews();
} else {
Toast.makeText(MainActivity.this, "There is nothing to delete", Toast.LENGTH_SHORT).show();
}
}
counter = 0;
}
})
.setNegativeButton("No", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
})
.show();
return true;
}
return super.onOptionsItemSelected(item);
}
public void addSemesterButton(int id) {
Display display = getWindowManager().getDefaultDisplay();
Point size = new Point();
display.getSize(size);
double width = (size.x) / 3;
semesterButton = new Button(MainActivity.this);
semesterButton.setId(id + 1);
semesterButton.setText("Semester " + (id + 1));
semesterButton.setBackgroundColor(getColor(R.color.colorPrimary));
semesterButton.setTextColor(Color.WHITE);
portraitLayoutParams.setMargins(24, 24, 24, 24);
if (MainActivity.this.getResources().getBoolean(R.bool.is_landscape)) {
GridLayout.LayoutParams params = new GridLayout.LayoutParams();
params.setMargins(24, 24, 24, 24);
params.width = (int) width;
params.height = GridLayout.LayoutParams.WRAP_CONTENT;
semesterButton.setLayoutParams(params);
semesterGridLayout.addView(semesterButton);
} else if (!MainActivity.this.getResources().getBoolean(R.bool.is_landscape)) {
semesterLayout.addView(semesterButton);
semesterButton.setLayoutParams(portraitLayoutParams);
}
setOnLongClickListenerForSemesterButton();
setOnClickListenerForSemesterButton(counter);
}
public void onFloatActionButtonClick(View view) {
if (counter < 8) {
addSemesterButton(counter);
counter++;
setOnLongClickListenerForSemesterButton();
} else if (counter == 8) {
Toast.makeText(MainActivity.this, "You cannot add more than 8 semesters", Toast.LENGTH_SHORT).show();
} else if (counter == 0) {
}
}
@Override
public void onSaveInstanceState(Bundle savedInstanceState) {
savedInstanceState.putInt("counter", counter);
super.onSaveInstanceState(savedInstanceState);
}
private void setOnClickListenerForSemesterButton(int id){
semesterButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(MainActivity.this, SemesterBuilderActivity.class);
intent.putExtra("someKey", 1);
startActivity(intent);
}
});
}
private void setOnLongClickListenerForSemesterButton() {
semesterButton.setOnLongClickListener(new View.OnLongClickListener() {
@Override
public boolean onLongClick(View v) {
final Button b = (Button) v;
b.setTag(b.getText().toString());
b.setBackgroundColor(Color.RED);
b.setText("Delete");
AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);
builder.setTitle("Delete entry");
builder.setMessage("Are you sure you want to delete this entry?");
builder.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
if (MainActivity.this.getResources().getBoolean(R.bool.is_landscape)) {
semesterGridLayout.removeView(b);
for (int i = 0; i < semesterGridLayout.getChildCount(); i++) {
((Button) semesterGridLayout.getChildAt(i)).setText("Semester " + (i + 1));
}
} else if (!MainActivity.this.getResources().getBoolean(R.bool.is_landscape)) {
semesterLayout.removeView(b);
for (int i = 0; i < semesterLayout.getChildCount(); i++) {
((Button) semesterLayout.getChildAt(i)).setText("Semester " + (i + 1));
}
}
counter--;
}
});
builder.setNegativeButton("No", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
b.cancelLongPress();
b.setBackgroundColor(ContextCompat.getColor(MainActivity.this, R.color.colorPrimary));
b.setText(b.getTag().toString());
dialog.cancel();
}
});
builder.show();
return true;
}
});
}
}
这是我的合同类：
public final class SemesterContract {
private SemesterContract(){}
public static final class SemesterEntry implements BaseColumns{
public static final String TABLE_NAME = "semesters";
public static final String _ID = BaseColumns._ID;
public static final String COLUMN_SEMESTER_NAME = "semester";
}
}
最后这是我的数据库助手：
public class SemesterDBHelper extends SQLiteOpenHelper{
public SemesterDBHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {
super(context, name, factory, version);
}
public static final String DATABASE_NAME = "semesters.db";
public static final int DATABASE_VERSION = 1;
@Override
public void onCreate(SQLiteDatabase db) {
String SQL_CREATE_SEMESTER_TABLE = "CREATE TABLE " + SemesterContract.SemesterEntry.TABLE_NAME + " ("
+ SemesterContract.SemesterEntry._ID + " INTEGER PRIMARY KEY AUTOINCREMENT, "
+ SemesterContract.SemesterEntry.COLUMN_SEMESTER_NAME + " TEXT NOT NULL";
db.execSQL(SQL_CREATE_SEMESTER_TABLE);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
}
我感谢所有的帮助。