Android 从服务访问应用程序类

为了将值存储为全局变量，我了解到可以使用应用程序类。我打算从主活动中获取用户名和密码，将它们存储在应用程序类变量中并启动一个新活动，然后在新活动中启动的服务中获取这些值，但是，使用我在应用程序类中定义的getter方法，我会得到空值

我的应用程序类：

public class MyApp extends Application
{
  private String uid;
  private String upwd;

  @Override
  public void onCreate()
  {
      super.onCreate();
  } 

  public void setUID(String value)
  {
      uid = value;
  }

  public void setPWD(String value)
  {
      upwd = value; 
  }

  public String getUID()
  {
      return uid;
  }

  public String getPWD()
  {
      return upwd;
  }
}

  public void setvalues()
  {
        unameval = Unametxtfield.getText().toString();
        pswrdval =  Pswrdtxtfield.getText().toString();     
        ((MyApp)this.getApplicationContext()).setUID(unameval);
        ((MyApp)this.getApplicationContext()).setPWD(pswrdval);
  }

public void fetchvalues()
{
      String uname = ((MyApp).getApplicationContext()).getUID();
      String upswrd = ((MyApp).getApplicationContext()).getPWD();
}

<application
        android:name="MyApp"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >

    <!-- A Service here -->
     <service
        android:name="Service1"
        android:process=":myapp_service1" >
    </service> 


    <!-- A service in which I do the fetching of uname and pswd -->
     <service 
        android:name="Service2"
        android:process=":myapp_Service2" >
     </service>

    <activity
        android:name=".Second_Activity"
        android:exported="false"
        android:label="@string/activityname" >
        <intent-filter>
            <action android:name="android.intent.action.DEFAULT" />
        </intent-filter>
    </activity>

    <activity
        android:name=".MainActivity"
        android:label="@string/Firstactivity" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>

</application>

在我的主要活动中：

public class MyApp extends Application
{
  private String uid;
  private String upwd;

  @Override
  public void onCreate()
  {
      super.onCreate();
  } 

  public void setUID(String value)
  {
      uid = value;
  }

  public void setPWD(String value)
  {
      upwd = value; 
  }

  public String getUID()
  {
      return uid;
  }

  public String getPWD()
  {
      return upwd;
  }
}

  public void setvalues()
  {
        unameval = Unametxtfield.getText().toString();
        pswrdval =  Pswrdtxtfield.getText().toString();     
        ((MyApp)this.getApplicationContext()).setUID(unameval);
        ((MyApp)this.getApplicationContext()).setPWD(pswrdval);
  }

public void fetchvalues()
{
      String uname = ((MyApp).getApplicationContext()).getUID();
      String upswrd = ((MyApp).getApplicationContext()).getPWD();
}

<application
        android:name="MyApp"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >

    <!-- A Service here -->
     <service
        android:name="Service1"
        android:process=":myapp_service1" >
    </service> 


    <!-- A service in which I do the fetching of uname and pswd -->
     <service 
        android:name="Service2"
        android:process=":myapp_Service2" >
     </service>

    <activity
        android:name=".Second_Activity"
        android:exported="false"
        android:label="@string/activityname" >
        <intent-filter>
            <action android:name="android.intent.action.DEFAULT" />
        </intent-filter>
    </activity>

    <activity
        android:name=".MainActivity"
        android:label="@string/Firstactivity" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>

</application>

服务内部我的第二个活动：

public class MyApp extends Application
{
  private String uid;
  private String upwd;

  @Override
  public void onCreate()
  {
      super.onCreate();
  } 

  public void setUID(String value)
  {
      uid = value;
  }

  public void setPWD(String value)
  {
      upwd = value; 
  }

  public String getUID()
  {
      return uid;
  }

  public String getPWD()
  {
      return upwd;
  }
}

  public void setvalues()
  {
        unameval = Unametxtfield.getText().toString();
        pswrdval =  Pswrdtxtfield.getText().toString();     
        ((MyApp)this.getApplicationContext()).setUID(unameval);
        ((MyApp)this.getApplicationContext()).setPWD(pswrdval);
  }

public void fetchvalues()
{
      String uname = ((MyApp).getApplicationContext()).getUID();
      String upswrd = ((MyApp).getApplicationContext()).getPWD();
}

<application
        android:name="MyApp"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >

    <!-- A Service here -->
     <service
        android:name="Service1"
        android:process=":myapp_service1" >
    </service> 


    <!-- A service in which I do the fetching of uname and pswd -->
     <service 
        android:name="Service2"
        android:process=":myapp_Service2" >
     </service>

    <activity
        android:name=".Second_Activity"
        android:exported="false"
        android:label="@string/activityname" >
        <intent-filter>
            <action android:name="android.intent.action.DEFAULT" />
        </intent-filter>
    </activity>

    <activity
        android:name=".MainActivity"
        android:label="@string/Firstactivity" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>

</application>

Android清单：

public class MyApp extends Application
{
  private String uid;
  private String upwd;

  @Override
  public void onCreate()
  {
      super.onCreate();
  } 

  public void setUID(String value)
  {
      uid = value;
  }

  public void setPWD(String value)
  {
      upwd = value; 
  }

  public String getUID()
  {
      return uid;
  }

  public String getPWD()
  {
      return upwd;
  }
}

  public void setvalues()
  {
        unameval = Unametxtfield.getText().toString();
        pswrdval =  Pswrdtxtfield.getText().toString();     
        ((MyApp)this.getApplicationContext()).setUID(unameval);
        ((MyApp)this.getApplicationContext()).setPWD(pswrdval);
  }

public void fetchvalues()
{
      String uname = ((MyApp).getApplicationContext()).getUID();
      String upswrd = ((MyApp).getApplicationContext()).getPWD();
}

<application
        android:name="MyApp"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >

    <!-- A Service here -->
     <service
        android:name="Service1"
        android:process=":myapp_service1" >
    </service> 


    <!-- A service in which I do the fetching of uname and pswd -->
     <service 
        android:name="Service2"
        android:process=":myapp_Service2" >
     </service>

    <activity
        android:name=".Second_Activity"
        android:exported="false"
        android:label="@string/activityname" >
        <intent-filter>
            <action android:name="android.intent.action.DEFAULT" />
        </intent-filter>
    </activity>

    <activity
        android:name=".MainActivity"
        android:label="@string/Firstactivity" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>

</application>

---

注意：我在某个地方读到，当您在多个进程上使用应用程序类（我想我正在这样做）时，应用程序类不会工作，这是真的吗？

使用还是使用。

这是真的。您不能在多个进程中使用此方法。我已经切换到共享首选项并使其正常工作。没有问题，但我想了解早期方法不起作用的原因，无论如何，感谢Singleton也不起作用。与应用程序对象的原因相同：不同的进程意味着不同的VM实例。它们不能直接通信并共享相同的内存空间。服务是否作为一个独立进程运行？