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我有一个回调类 gaGPS，我认为这是一个在正常活动中可以正常工作的上下文，但是当我在 Fragment 中使用它时它会失败

这是我的接口类

Public class gaGPS extends Service implements LocationListener {

private final Context mContext;

// Declaring a Location Manager
protected LocationManager locationManager;

private gaGPSinterface gpsu;

public interface gaGPSinterface {
    public void locationChanged(Location newloc);
}


public gaGPS(Context c, gaGPSinterface gpsiface) {
    mCallback = gpsiface;
    //mContext = (Context) gpsiface;
    mContext = c;


    locationManager = (LocationManager) mContext.getSystemService(Context.LOCATION_SERVICE);
}

剪断

我正在使用这个 FragmentActivity 类启动 Fragment

public class gaDetailsActivity extends FragmentActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.gpsfragment);

}

这是 gpsfragment.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".gpsfragment" >
<fragment
    android:id="@+id/gpsTestFragLayout"
    android:name="id.wilsononline.gcadroid.gpsfragment"
    android:layout_width="0dp"
    android:layout_height="match_parent"
    android:layout_weight="1" />

以下是我正在使用的片段

public class gpsfragment extends Fragment implements gaGPS.gaGPSinterface {

private gaGPS gps;

@Override
public void locationChanged(Location newloc) {
    // TODO Auto-generated method stub

}

@Override
public void onAttach(Activity activity) {
    // TODO Auto-generated method stub
    super.onAttach(activity);
}


@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    View rootView = inflater.inflate(R.layout.gpsdetails, container, false);
    ((TextView) rootView.findViewById(R.id.gpsText1)).setText("testing fragment");

    Context c = getActivity().getApplicationContext();

    gps = new gaGPS(c, (gaGPSinterface) getActivity());

    return rootView;
}

}

我得到的错误是： java.lang.ClassCastException: com.test.app.gpsfragment cannot be cast to android.content.Context

更全面的输出：

E/AndroidRuntime( 3118): Caused by: android.view.InflateException: Binary XML file line #8: Error inflating class fragment
E/AndroidRuntime( 3118):        at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:704)
E/AndroidRuntime( 3118):        at android.view.LayoutInflater.rInflate(LayoutInflater.java:746)
E/AndroidRuntime( 3118):        at android.view.LayoutInflater.inflate(LayoutInflater.java:489)
E/AndroidRuntime( 3118):        at android.view.LayoutInflater.inflate(LayoutInflater.java:396)
E/AndroidRuntime( 3118):        at android.view.LayoutInflater.inflate(LayoutInflater.java:352)
E/AndroidRuntime( 3118):        at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:256)
E/AndroidRuntime( 3118):        at android.com.test.app.Activity.setContentView(Activity.java:1867)
E/AndroidRuntime( 3118):        at id.wilsononline.gcadroid.gaDetailsActivity.onCreate(gaDetailsActivity.java:12)
E/AndroidRuntime( 3118):        at android.com.test.app.Activity.performCreate(Activity.java:5008)
E/AndroidRuntime( 3118):        at android.com.test.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)
E/AndroidRuntime( 3118):        at android.com.test.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023)
E/AndroidRuntime( 3118):        ... 11 more
E/AndroidRuntime( 3118): Caused by: java.lang.ClassCastException: com.test.com.test.app.gaDetailsActivity cannot be cast to id.wilsononli
ne.gcadroid.gaGPS$gaGPSinterface
E/AndroidRuntime( 3118):        at com.test.com.test.app.gpsfragment.onCreateView(gpsfragment.java:49)
E/AndroidRuntime( 3118):        at android.support.v4.com.test.app.Fragment.performCreateView(Fragment.java:1460)
E/AndroidRuntime( 3118):        at android.support.v4.com.test.app.FragmentManagerImpl.moveToState(FragmentManager.java:884)
E/AndroidRuntime( 3118):        at android.support.v4.com.test.app.FragmentManagerImpl.moveToState(FragmentManager.java:1066)
E/AndroidRuntime( 3118):        at android.support.v4.com.test.app.FragmentManagerImpl.addFragment(FragmentManager.java:1168)
E/AndroidRuntime( 3118):        at android.support.v4.com.test.app.FragmentActivity.onCreateView(FragmentActivity.java:280)
E/AndroidRuntime( 3118):        at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:676)
E/AndroidRuntime( 3118):        ... 21 more
4

1 回答 1

1 
public gaGPS(gaGPSinterface gpsu) {
    this.mContext = (Context) gpsu;
    this.gpsu = gpsu;
    // ...
}

在这里，您尝试转换gpsu为Context. 它不是一个；这是一个Fragment。您应该分别通过Contextand gaGPSinterface：

public gaGPS(Context c, gaGPSinterface gpsu) {
    this.mContext = c;
    this.gpsu = gpsu;
    // ...
}

然后，使用.getActivity()（返回一个Activity，一个子类Context）从调用它Fragment：

gps = new gaGPS(getActivity(), this);
于 2013-01-23T23:51:39.960 回答