所以我有一个奇怪的问题。我有 2 项活动正在进行。其中一个活动显示了一个 ListView,它的数据是通过一个长的 Extra 抓取的,我使用它通过 database.query 中的 WHERE 子句获取结果。当单击 ListView 项时调用另一个 Activity,允许某人为 ListView 添加一些内容到数据库中。
活动名称是DaysActivity.java
(带有列表视图的活动)和DayAddActivity.java
(允许某人添加一天的活动,然后显示在列表视图中DaysActivity.java
)。
我遇到的问题是,当我finish()
DayAddActivity.java
返回DaysActivity
并且 ListView 仍然完全填充时。但是,如果我点击后退按钮DayAddActivity.java
(带有我的应用程序图标的操作栏中标题左侧的按钮),当它返回 DaysActivity.java 时,ListView 为空/消失。
这是两者的代码:
DaysActivity.java:
package com.gauvion.gfit;
import android.annotation.SuppressLint;
import android.app.ListActivity;
import android.content.Intent;
import android.content.SharedPreferences;
import android.database.Cursor;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.widget.SimpleCursorAdapter;
import android.widget.Toast;
public class DaysActivity extends ListActivity {
private DaysDataSource datasource;
private SimpleCursorAdapter dataAdapter;
private boolean isEditing = false;
private Toast toast_deleted;
private String[] columns = new String[] { MySQLiteHelper.COLUMN_NAME, MySQLiteHelper.COLUMN_DAY };
private int[] to;
private long routineDataID;
private String routineDataName;
@SuppressLint("ShowToast")
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_days);
routineDataID = getIntent().getLongExtra("routineDataID", 0);
routineDataName = getIntent().getStringExtra("routineDataName");
setTitle(routineDataName);
toast_deleted = Toast.makeText(this, "", Toast.LENGTH_SHORT);
datasource = new DaysDataSource(this);
datasource.open();
Cursor cursor = datasource.fetchAllDays(routineDataID);
to = new int[] { R.id.listitem_day_name, R.id.listitem_day_day };
dataAdapter = new SimpleCursorAdapter(this, R.layout.listitem_day, cursor, columns, to, 0);
setListAdapter(dataAdapter);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.activity_days, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
Cursor cursor = datasource.fetchAllDays(routineDataID);
switch (item.getItemId()) {
case R.id.button_days_add:
Intent startDayAdd = new Intent(this, DayAddActivity.class);
startDayAdd.putExtra("routineDataID", routineDataID);
this.startActivity(startDayAdd);
return true;
case R.id.button_days_edit:
to = new int[] { R.id.listitem_day_edit_name, R.id.listitem_day_edit_day };
dataAdapter = new SimpleCursorAdapter(this, R.layout.listitem_day_edit, cursor, columns, to, 0);
setListAdapter(dataAdapter);
isEditing = true;
invalidateOptionsMenu();
return true;
case R.id.button_days_edit_done:
to = new int[] { R.id.listitem_day_name, R.id.listitem_day_day };
dataAdapter = new SimpleCursorAdapter(this, R.layout.listitem_day, cursor, columns, to, 0);
setListAdapter(dataAdapter);
isEditing = false;
invalidateOptionsMenu();
return true;
default:
return super.onOptionsItemSelected(item);
}
}
@Override
public boolean onPrepareOptionsMenu(Menu menu) {
super.onPrepareOptionsMenu(menu);
menu.findItem(R.id.button_days_edit).setVisible(!isEditing);
menu.findItem(R.id.button_days_edit_done).setVisible(isEditing);
return true;
}
@Override
protected void onResume() {
datasource.open();
Cursor cursor = datasource.fetchAllDays(routineDataID);
dataAdapter.changeCursor(cursor);
super.onResume();
}
@Override
protected void onPause() {
datasource.close();
super.onPause();
}
}
DayAddActivity.java:
package com.gauvion.gfit;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Spinner;
import android.widget.Toast;
import android.support.v4.app.NavUtils;
public class DayAddActivity extends Activity {
private RoutinesDataSource datasource;
private EditText dayName;
private Spinner dayDay;
private Button saveButton;
private long routineDataID;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_day_add);
routineDataID = getIntent().getLongExtra("routineDataID", 0);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.activity_day_add, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
NavUtils.navigateUpFromSameTask(this);
return true;
}
return super.onOptionsItemSelected(item);
}
public void cancelDay(View view) {
this.finish();
}
}
cancelDay()
当在 中单击“取消”按钮时调用该函数activity_day_add.xml
。就像我说的,当我单击 内部的“取消”按钮时DayAddActivity.java
,它会返回DaysActivity.java
并且 ListView 很好。所有数据都在那里。但是,如果我按下操作栏中的后退按钮(包含后退箭头的按钮和 Activity 标题旁边的我的应用程序图标)ListView 为DaysActivity.java
空/消失,并且标题也是空的(因为这也生成通过一个额外的字符串值)。