我一直在研究我的应用程序，并且我需要了解Activity生命周期，我认为我没有得到它。我所拥有的是一个带有七个按钮的活动。当用户按下按钮时，它会打开一个listActivity，用户可以在其中选择列表中的项目，标题将被发送回调用的Activity，并且调用活动会在按钮上的文本旁边添加标题。 （它使用的方法是在switch语句中，它取决于请求代码返回给它 - 我认为它对我的目的来说有点弱。）但是如果用户离开活动并返回到它，通过后退按钮或任何其他按钮，当他们返回时没有任何额外信息 - 剩下的就是带有原始文本的七个按钮。我想留下这些信息 - 我该怎么做？
以下是调用Activity：
的代码package com.dinner.live;
import android.app.Activity;
import android.app.ListActivity;
import android.content.Intent;
import android.database.Cursor;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.SimpleCursorAdapter;
import android.widget.Toast;
public class PlanMenu extends Activity {
static final private int CHOOSE_MONDAY = 0;
static final private int CHOOSE_TUESDAY = 1;
static final private int CHOOSE_WEDNESDAY = 2;
static final private int CHOOSE_THURSDAY = 3;
static final private int CHOOSE_FRIDAY = 4;
static final private int CHOOSE_SATURDAY = 5;
static final private int CHOOSE_SUNDAY = 6;
private boolean ButtonPushed = false;
private NotesDbAdapter mDbHelper;
private MenuDbAdapter menuDbHelper;
private Long menuID;
private String mTitleText;
private String m;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.plan_menu);
Toast.makeText(this, "Choose a day to pick a meal for!", Toast.LENGTH_LONG).show();
mDbHelper = new NotesDbAdapter(this);
mDbHelper.open();
menuDbHelper = new MenuDbAdapter(this);
menuDbHelper.open();
}
public void mButtonHandler(View target)
{
switch(target.getId())
{
case R.id.monday:
if(ButtonPushed == false)
{
// Create new intent object and tell it to call the ColorPicker class
Intent monday = new Intent(this, PlanMenuList.class);
// Start ColorPicker as a new activity and wait for the result
startActivityForResult(monday, CHOOSE_MONDAY);
ButtonPushed = true;
break;
}
else
Toast.makeText(this, "That button has already been pushed." , Toast.LENGTH_LONG).show();
break;
case R.id.tuesday:
// Create new intent object and tell it to call the ColorPicker class
Intent tuesday = new Intent(this, PlanMenuList.class);
// Start ColorPicker as a new activity and wait for the result
startActivityForResult(tuesday, CHOOSE_TUESDAY);
break;
case R.id.wednesday:
// Create new intent object and tell it to call the ColorPicker class
Intent wednesday = new Intent(this, PlanMenuList.class);
// Start ColorPicker as a new activity and wait for the result
startActivityForResult(wednesday, CHOOSE_WEDNESDAY);
break;
case R.id.thursday:
// Create new intent object and tell it to call the ColorPicker class
Intent thursday = new Intent(this, PlanMenuList.class);
// Start ColorPicker as a new activity and wait for the result
startActivityForResult(thursday, CHOOSE_THURSDAY);
break;
case R.id.friday:
// Create new intent object and tell it to call the ColorPicker class
Intent friday = new Intent(this, PlanMenuList.class);
// Start ColorPicker as a new activity and wait for the result
startActivityForResult(friday, CHOOSE_FRIDAY);
break;
case R.id.saturday:
// Create new intent object and tell it to call the ColorPicker class
Intent saturday = new Intent(this, PlanMenuList.class);
// Start ColorPicker as a new activity and wait for the result
startActivityForResult(saturday, CHOOSE_SATURDAY);
break;
case R.id.sunday:
// Create new intent object and tell it to call the ColorPicker class
Intent sunday = new Intent(this, PlanMenuList.class);
// Start ColorPicker as a new activity and wait for the result
startActivityForResult(sunday, CHOOSE_SUNDAY);
break;
}
}
@Override
protected void onActivityResult(int requestCode, int resultCode,
Intent intent) {
super.onActivityResult(requestCode, resultCode, intent);
if(resultCode == RESULT_OK){
switch(requestCode)
{
case CHOOSE_MONDAY:
menuID = intent.getExtras().getLong("newRowId");
menuDbHelper.fetchMenu(menuID);
populateFields();
//String label = intent.getExtras().getString("menuString");//intent.getExtras().getLong(MenuDbAdapter.KEY_ROWID);
Button tv = (Button)findViewById(R.id.monday);
m = mTitleText;
tv.setText("Monday" + " - " + mTitleText);
break;
case CHOOSE_TUESDAY:
String labelT = intent.getExtras().getString("menuString");//intent.getExtras().getLong(MenuDbAdapter.KEY_ROWID);
Button tvT = (Button)findViewById(R.id.tuesday);
tvT.setText("Tuesday" + " - " + labelT);
break;
case CHOOSE_WEDNESDAY:
String labelW = intent.getExtras().getString("menuString");//intent.getExtras().getLong(MenuDbAdapter.KEY_ROWID);
Button tvW = (Button)findViewById(R.id.wednesday);
tvW.setText("Wednesday" + " - " + labelW);
break;
case CHOOSE_THURSDAY:
String labelTh = intent.getExtras().getString("menuString");//intent.getExtras().getLong(MenuDbAdapter.KEY_ROWID);
Button tvTh = (Button)findViewById(R.id.thursday);
tvTh.setText("Thursday" + " - " + labelTh);
break;
case CHOOSE_FRIDAY:
String labelFriday = intent.getExtras().getString("menuString");//intent.getExtras().getLong(MenuDbAdapter.KEY_ROWID);
Button tvFriday = (Button)findViewById(R.id.friday);
tvFriday.setText("Friday" + " - " + labelFriday);
break;
case CHOOSE_SATURDAY:
String labelS = intent.getExtras().getString("menuString");//intent.getExtras().getLong(MenuDbAdapter.KEY_ROWID);
Button tvS = (Button)findViewById(R.id.saturday);
tvS.setText("Saturday" + " - " + labelS);
break;
case CHOOSE_SUNDAY:
String labelSa = intent.getExtras().getString("menuString");//intent.getExtras().getLong(MenuDbAdapter.KEY_ROWID);
Button tvSa = (Button)findViewById(R.id.sunday);
tvSa.setText("Sunday" + " - " + labelSa);
break;
}
}
}
private void populateFields() {
if (menuID != null) {
Cursor note = menuDbHelper.fetchMenu(menuID);
startManagingCursor(note);
mTitleText = (note.getString(
note.getColumnIndexOrThrow(MenuDbAdapter.KEY_TITLE)));
}
}
}
答案 0 :(得分：1)
取决于。通常，您需要覆盖onSaveInstanceState（）并将所有数据保存到Bundle（它是一个简单的键/值对事件）并在onCreate（）（或onRestoreInstanceState（）中重新创建它，如果您想要分离代码出）。
但是，这主要是因为用户更改了方向而销毁和重新创建应用的情况。
如果你想要数据是持久的（即你去那个活动，回到调用活动，甚至可能完全切换到另一个应用程序，然后再回来），我建议将所有内容保存到onPause（）中的SharedPreferences中然后在onResume（）中将其放回原位。这样，数据将处于持久存储状态，甚至比系统重置更长。