该应用：我有一个可以创建多台计算机的应用：
这些机器的每个我必须让用户分别输入收入。
问题：我需要 SUM 从每台机器输入的所有收入（ money，date，note，machines_id ） AND 在另一个Activity中的TextView中显示它。
我的问题：如何将getIncomeOfMachine方法的rawQuery中的数据传输到另一个Activity？
我尝试了什么：使用DBHelper类中的Bundles，Intents和SharedPreferences。
DBHelper
public class DBHelpter extends SQLiteOpenHelper {
private static final String DB_NAME = "machines.db";
private static final int DB_VERSION = 1;
public static final String TABLE_MACHINES = "machines";
public static final String MACHINES_COLUMN_NAME = "name";
public static final String MACHINES_COLUMN_LOCATION = "location";
public static final String MACHINES_ID = "id";
public static final String TABLE_INCOME = "income";
public static final String INCOME_COLUMN_MONEY = "money";
public static final String INCOME_COLUMN_DATE = "date";
public static final String INCOME_COLUMN_NOTE = "note";
public static final String INCOME_ID = "id";
public static final String INCOME_COLUMN_MACHINES_ID = "machines_id";
private Context mContext;
public DBHelpter(Context context) {
super(context, DB_NAME, null, DB_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
String query1 = String.format("CREATE TABLE " + TABLE_MACHINES + "("
+ MACHINES_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, "
+ MACHINES_COLUMN_NAME + " TEXT NOT NULL, "
+ MACHINES_COLUMN_LOCATION + " TEXT NOT NULL)",
TABLE_MACHINES, MACHINES_COLUMN_NAME, MACHINES_COLUMN_LOCATION, MACHINES_ID);
String query2 = String.format("CREATE TABLE " + TABLE_INCOME + "("
+ INCOME_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, "
+ INCOME_COLUMN_MONEY + " REAL NOT NULL, "
+ INCOME_COLUMN_DATE + " DATE NOT NULL, "
+ INCOME_COLUMN_NOTE + " TEXT NOT NULL, "
+ INCOME_COLUMN_MACHINES_ID + " INTEGER NOT NULL)",
TABLE_INCOME, INCOME_ID, INCOME_COLUMN_MONEY, INCOME_COLUMN_DATE, INCOME_COLUMN_NOTE, INCOME_COLUMN_MACHINES_ID);
db.execSQL(query1);
db.execSQL(query2);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
String query1 = String.format("DROP TABLE IF EXISTS " + TABLE_MACHINES);
String query2 = String.format("DROP TABLE IF EXISTS " + TABLE_INCOME);
db.execSQL(query1);
db.execSQL(query2);
onCreate(db);
}
public void insertNewMachine(String name, String location){
SQLiteDatabase db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(MACHINES_COLUMN_NAME, name);
values.put(MACHINES_COLUMN_LOCATION, location);
db.insertWithOnConflict(TABLE_MACHINES, null, values, SQLiteDatabase.CONFLICT_REPLACE);
db.close();
}
public void insertNewIncome(Double money, String date, String note, long machines_id){
SQLiteDatabase db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(INCOME_COLUMN_MONEY, money);
values.put(INCOME_COLUMN_DATE, date);
values.put(INCOME_COLUMN_NOTE, note);
values.put(INCOME_COLUMN_MACHINES_ID, machines_id);
db.insertWithOnConflict(TABLE_INCOME, null, values, SQLiteDatabase.CONFLICT_REPLACE);
db.close();
}
public void getIncomeOfMachine(long machinesId){
SQLiteDatabase db = getReadableDatabase();
Cursor cursor = db.rawQuery("SELECT machines_id, SUM(money) AS total FROM income WHERE machines_id = "+machinesId+"", null);
while (cursor.moveToFirst()){
String totalAmount = String.valueOf(cursor.getInt(0));
SharedPreferences mSharedPreferences = mContext.getSharedPreferences(PREFS_NAME, Context.MODE_PRIVATE);
SharedPreferences.Editor mEditor = mSharedPreferences.edit();
mEditor.putString("total_amount", totalAmount);
mEditor.commit();
}
cursor.close();
db.close();
}
public ArrayList<MachinesClass> getAllMachines(){
ArrayList<MachinesClass> machinesList = new ArrayList<>();
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.rawQuery("SELECT * FROM "+ TABLE_MACHINES, null);
while (cursor.moveToNext()){
final long id = cursor.getLong(cursor.getColumnIndex(MACHINES_ID));
final String name = cursor.getString(cursor.getColumnIndex(MACHINES_COLUMN_NAME));
final String location = cursor.getString(cursor.getColumnIndex(MACHINES_COLUMN_LOCATION));
machinesList.add(new MachinesClass(id, name, location));
}
cursor.close();
db.close();
return machinesList;
}
RecyclerViewAdapter
public class MachinesAdapter extends RecyclerView.Adapter<MachinesAdapter.ViewHolder> {
private ArrayList<MachinesClass> machinesList;
private LayoutInflater mInflater;
private DBHelpter mDBHelpter;
private Context mContext;
public static final String PREFS_NAME = "MyPrefsFile";
public MachinesAdapter(Context mContext, ArrayList<MachinesClass> machinesList){
this.mContext = mContext;
this.machinesList = machinesList;
}
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.machines_list, parent, false);
return new ViewHolder(view);
}
@Override
public void onBindViewHolder(ViewHolder holder, final int position) {
holder.mLocation.setText(machinesList.get(position).getLocation());
holder.v.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
SharedPreferences mSharedPreferences = mContext.getSharedPreferences(PREFS_NAME, Context.MODE_PRIVATE);
SharedPreferences.Editor mEditor = mSharedPreferences.edit();
mEditor.putString("location", machinesList.get(position).getLocation());
mEditor.putLong("machines_id", machinesList.get(position).getId());
mEditor.commit();
Bundle bundle = new Bundle();
bundle.putString("location", machinesList.get(position).getLocation());
Intent intent = new Intent(v.getContext(), MachineInfo.class);
intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
intent.putExtras(bundle);
mContext.startActivity(intent);
}
});
}
@Override
public int getItemCount() {
return machinesList != null ? machinesList.size() : 0;
}
public class ViewHolder extends RecyclerView.ViewHolder {
public TextView mLocation, mMoney;
public LinearLayout mLinearLayout;
public View v;
public ViewHolder(View v) {
super(v);
mLinearLayout = (LinearLayout) v.findViewById(R.id.linearLayout);
mLocation = (TextView) v.findViewById(R.id.tvLocation);
mMoney = (TextView) v.findViewById(R.id.tvMoney);
this.v = v;
}
}
}
MachineInfo
public class MachineInfo extends AppCompatActivity {
private TextView mLocation, mMoney, mNotes;
private DBHelpter mDBHelpter;
private FloatingActionButton mFAB;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_machine_info);
mDBHelpter = new DBHelpter(getApplicationContext());
mLocation = (TextView) findViewById(R.id.tvLocation);
mMoney = (TextView) findViewById(R.id.tvMoney);
mNotes = (TextView) findViewById(R.id.tvNotes);
mFAB = (FloatingActionButton) findViewById(R.id.fabAddIncome);
SharedPreferences mSharedPreferences = getSharedPreferences(PREFS_NAME, Context.MODE_PRIVATE);
String total_amount = mSharedPreferences.getString("total_amount", null);
mMoney.setText(total_amount);
String location = mSharedPreferences.getString("location", null);
mLocation.setText(location);
mFAB.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent i = new Intent(getApplicationContext(), IncomeCreation.class);
startActivity(i);
}
});
}
}
如果您需要任何其他活动或布局，请告诉我们！
答案 0 :(得分：1)
首先，我建议更改为getIncomeOfMachine()。由于此方法位于DBHelper中，因此它应仅负责与数据库交互。它应该不了解有关SharedPreferences或Activity的任何信息。相反，它应该返回从数据库中检索的值，并让调用者决定如何处理该值。由于您知道生成的Cursor中只有一行，因此您不需要循环。只需移动到第一行，获取总数，然后返回。
其次，由于您只是将一个值传递给某个活动，并且您可能不需要将其永久存储以供以后使用，因此您应该使用Intent而不是SharedPreferences。 Starting Another Activity有一个向另一个活动发送值的明显示例。如果您在应用中使用此示例时遇到问题，请随时发布一个新问题，说明您的操作并解释您遇到的问题。