检索共享首选项

Question

我有两个活动A和B。

B:是将所有设置保存在共享首选项中的设置活动。

A：是主要活动，我检索保存在B活动中的共享偏好

问题是，如果用户第一次使用该应用程序并启动A活动（强制关闭）。

我认为，因为还没有保存共享偏好。。。

A活动：

public class DawaaActivity extends ListActivity implements View.OnClickListener {
Button add;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
SharedPreferences emportPref = getSharedPreferences("dawaaData",MODE_PRIVATE);
if (emportPref.getInt("exists", 0) == 1){
String dawaaList[] = {emportPref.getString("subject", null)};
setListAdapter(new ArrayAdapter<String>(DawaaActivity.this,
android.R.layout.simple_list_item_1,dawaaList));
}
initialaiz();
}
private void initialaiz() {
add = (Button) findViewById(R.id.button3);
add.setOnClickListener(this);
}
public void onClick(View v) {
Intent data = new Intent(DawaaActivity.this,SettingActivity.class);
startActivity(data);
}
}

B活动：

public class SettingActivity extends Activity implements View.OnClickListener {
EditText et;
EditText et1;
Spinner list;
TimePicker startTime;
Button save;
Button cancel;
private SharedPreferences exportPref;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.setting);
initialaiz();
}
private void initialaiz() {
et = (EditText) findViewById(R.id.text);
et1 = (EditText) findViewById(R.id.text1);
list = (Spinner) findViewById(R.id.spinner);
startTime = (TimePicker) findViewById(R.id.timePicker);
save = (Button) findViewById(R.id.save);
cancel = (Button) findViewById(R.id.cancel);
save.setOnClickListener(this);
cancel.setOnClickListener(this);
}
public void onClick(View v) {
switch(v.getId()){
case R.id.save:
save();
Intent transferData = new Intent(SettingActivity.this,DawaaActivity.class);
startActivity(transferData);
break;
case R.id.cancel:
finish();
break;
}
}
private void save() {
exportPref = getSharedPreferences("dawaaData",MODE_PRIVATE);
SharedPreferences.Editor editor = exportPref.edit();
editor.putString("subject", et.getText().toString());
editor.putString("dosesC", et1.getText().toString());
editor.putString("doses", list.getSelectedItem().toString());
editor.putInt("hour", startTime.getCurrentHour());
editor.putInt("minute", startTime.getCurrentMinute());
editor.putInt("exists", 1);
editor.commit();
Toast.makeText(SettingActivity.this,"data has been saved" ,Toast.LENGTH_SHORT).show();
}
}

我怎样才能解决这个问题？？？

编辑：

我在布局中添加ListView

我这样编辑这个类：

public class DawaaActivity extends Activity implements View.OnClickListener {
ListView myList;
SharedPreferences emportPref = getSharedPreferences("dawaaData",MODE_PRIVATE);
String dawaaList[] = {emportPref.getString("subject", "no data yet")};
myList = (ListView) findViewById(R.id.ListView);
myList.setAdapter(new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1, dawaaList));

这就是logcat：

08-28 14:56:41.112: E/AndroidRuntime(273):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2585)
08-28 14:56:41.112: E/AndroidRuntime(273):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
08-28 14:56:41.112: E/AndroidRuntime(273):  at android.app.ActivityThread.access$2300(ActivityThread.java:125)
08-28 14:56:41.112: E/AndroidRuntime(273):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
08-28 14:56:41.112: E/AndroidRuntime(273):  at android.os.Handler.dispatchMessage(Handler.java:99)
08-28 14:56:41.112: E/AndroidRuntime(273):  at android.os.Looper.loop(Looper.java:123)
08-28 14:56:41.112: E/AndroidRuntime(273):  at android.app.ActivityThread.main(ActivityThread.java:4627)
08-28 14:56:41.112: E/AndroidRuntime(273):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
08-28 14:56:41.112: E/AndroidRuntime(273):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
08-28 14:56:41.112: E/AndroidRuntime(273):  at android.content.ContextWrapper.getSharedPreferences(ContextWrapper.java:146)
08-28 14:56:41.112: E/AndroidRuntime(273):  at android.app.Instrumentation.newActivity(Instrumentation.java:1021)
08-28 14:56:41.112: E/AndroidRuntime(273):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2577)
08-28 14:59:54.272: E/AndroidRuntime(303):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2585)
08-28 14:59:54.272: E/AndroidRuntime(303):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
08-28 14:59:54.272: E/AndroidRuntime(303):  at android.app.ActivityThread.access$2300(ActivityThread.java:125)
08-28 14:59:54.272: E/AndroidRuntime(303):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
08-28 14:59:54.272: E/AndroidRuntime(303):  at android.os.Handler.dispatchMessage(Handler.java:99)
08-28 14:59:54.272: E/AndroidRuntime(303):  at android.os.Looper.loop(Looper.java:123)
08-28 14:59:54.272: E/AndroidRuntime(303):  at android.app.ActivityThread.main(ActivityThread.java:4627)
08-28 14:59:54.272: E/AndroidRuntime(303):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
08-28 14:59:54.272: E/AndroidRuntime(303):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
08-28 14:59:54.272: E/AndroidRuntime(303):  at android.content.ContextWrapper.getSharedPreferences(ContextWrapper.java:146)
08-28 14:59:54.272: E/AndroidRuntime(303):  at android.app.Instrumentation.newActivity(Instrumentation.java:1021)
08-28 14:59:54.272: E/AndroidRuntime(303):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2577)
08-28 15:02:26.632: E/AndroidRuntime(331):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2585)

08-28 15:02:26.632:E/AndroidRuntime（331）：在android.app.ActivityThread.handleLaunchActivity（ActivityThreads.java:2679）08-28 15:02:26.632:E/AndroidRuntime（331）：在android.app.ActivityThread.access$2300（ActivityThreads.java:125）08-28 15:02:26.632:E/AndroidRuntime（331）：在android.app.ActivityThread$H.handleMessage（ActivityThread.java：2033）08-28 15:02:26.632:E/AndroidRuntime（331）：在android.os.Handler.dispatchMessage（Handler.java:99）08-28 15:02:26.632:E/AndroidRuntime（331）：在android.os.Looper.loop（Looper.java:123）08-28 15:02:26.632:E/AndroidRuntime（331）：在android.app.ActivityThread.main（ActivityThreads.java：4627）08-28 15:02:26.632:E/AndroidRuntime（331）：在com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run（ZygoteInit.java:868）08-28 15:02:26.632:E/AndroidRuntime（331）：在com.android.internal.os.ZygoteInit.main（ZygoteNit.java:626）08-28 15:02:26.632:E/AndroidRuntime（331）：在android.content.ContextWrapper.getSharedPreferences（ContextWrapper.java:146）08-28 15:02:26.632:E/AndroidRuntime（331）：在android.app.Instrumentation.newActivity（Instrumentation.java:1021）08-28 15:02:26.632:E/AndroidRuntime（331）：在android.app.ActivityThread.performLaunchActivity（ActivityThreads.java:2577）

Answer 1

问题可能在这里：

String dawaaList[] = {emportPref.getString("subject", null)};
setListAdapter(new ArrayAdapter<String>(DawaaActivity.this,
android.R.layout.simple_list_item_1, dawaaList));

如果你没有任何主题，你会得到一个null，然后可能在某个地方得到一个nullpointer。

尝试检查null，或者在null的情况下用一些东西初始化它，比如：

if (dawaaList[] == null) { 
   new String[]{"No subjects"}; 
}

请发布您的日志以获得进一步的帮助。

编辑：

你可以这样处理：

只需在布局中添加ListView

    <ListView
        android:id="@+id/myListView"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        />

并将其填充到活动中

    setContentView(R.layout.main);
    ListView listView = (ListView) findViewById(R.id.myListView);
    SharedPreferences pref = getSharedPreferences("dawaaData", MODE_PRIVATE);
    String items = pref.getString("subject", "item1,item2,item3");
    String[] listItems = items.split(",");
    listView.setAdapter(new ArrayAdapter<String>(this,  android.R.layout.simple_list_item_1, listItems));

我选择逗号作为分隔符，因为SharedPreferences无法存储数组。您应该使用Set和pref.getStringSet（来自api 11），或者序列化列表（json或任何东西）。

Answer 2

应用程序A会因为第一次没有初始化值而关闭。最简单的方法是将从SharedPreferences读取值的代码包装在try-catch（Throwablet）中

Answer 3

这两个函数将解决您的问题，第一个是保存您需要在类A中cal的首选项，您希望在其中存储值

public void saveSharedPreference() {
        SharedPreferences myPrefs = this.getSharedPreferences("myPrefs",
                MODE_WORLD_READABLE);
        SharedPreferences.Editor prefsEditor = myPrefs.edit();
        prefsEditor.putString(stringname, stringvalue);
        prefsEditor.commit();
    }

在你的B活动中，你必须调用LoadPreferences函数

private void LoadPreferences() {
        SharedPreferences sharedPreferences = this.getSharedPreferences(
                "myPrefs", MODE_WORLD_READABLE);
        String yourvariable= sharedPreferences.getString(name, "0"); // it will take 0 as default value if variable is empty and you can set you own default value  }