【发布时间】：2015-04-29 14:07:35
【问题描述】：
我使用 ViewPager 在一个片段中有两个片段。
有时我的应用程序崩溃并出现以下错误：
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.myapp/com.myapp.MyAcitivity}: android.support.v4.app.Fragment$InstantiationException: Unable to instantiate fragment com.fragments.MyFragment: make sure class name exists, is public, and has an empty constructor that is public
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2318)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2396)
at android.app.ActivityThread.access$800(ActivityThread.java:139)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1293)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:149)
at android.app.ActivityThread.main(ActivityThread.java:5257)
at java.lang.reflect.Method.invokeNative(Method.java)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:817)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:633)
at dalvik.system.NativeStart.main(NativeStart.java)
Caused by: android.support.v4.app.Fragment$InstantiationException: Unable to instantiate fragment com.fragments.MyFragment: make sure class name exists, is public, and has an empty constructor that is public
at android.support.v4.app.Fragment.instantiate(Fragment.java:413)
at android.support.v4.app.FragmentState.instantiate(Fragment.java:97)
at android.support.v4.app.FragmentManagerImpl.restoreAllState(FragmentManager.java:1801)
at android.support.v4.app.FragmentActivity.onCreate(FragmentActivity.java:213)
at android.support.v7.app.ActionBarActivity.onCreate(ActionBarActivity.java:97)
at com.buzzreel.MyActivity.onCreate(MyActivity.java:55)
at android.app.Activity.performCreate(Activity.java:5411)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2270)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2396)
at android.app.ActivityThread.access$800(ActivityThread.java:139)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1293)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:149)
at android.app.ActivityThread.main(ActivityThread.java:5257)
at java.lang.reflect.Method.invokeNative(Method.java)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:817)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:633)
at dalvik.system.NativeStart.main(NativeStart.java)
Caused by: java.lang.InstantiationException: can't instantiate class com.fragments.MyFragment; no empty constructor
at java.lang.Class.newInstanceImpl(Class.java)
at java.lang.Class.newInstance(Class.java:1208)
at android.support.v4.app.Fragment.instantiate(Fragment.java:402)
at android.support.v4.app.FragmentState.instantiate(Fragment.java:97)
at android.support.v4.app.FragmentManagerImpl.restoreAllState(FragmentManager.java:1801)
at android.support.v4.app.FragmentActivity.onCreate(FragmentActivity.java:213)
at android.support.v7.app.ActionBarActivity.onCreate(ActionBarActivity.java:97)
at com.buzzreel.MyActivity.onCreate(MyActivity.java:55)
at android.app.Activity.performCreate(Activity.java:5411)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2270)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2396)
at android.app.ActivityThread.access$800(ActivityThread.java:139)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1293)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:149)
at android.app.ActivityThread.main(ActivityThread.java:5257)
at java.lang.reflect.Method.invokeNative(Method.java)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:817)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:633)
at dalvik.system.NativeStart.main(NativeStart.java)
但我的片段类中有两个构造函数，如下所示：
public MyFragment(CustomObject custom) {
this.custom = custom;
}
public MyFragment() {
}
我的寻呼机适配器调用：
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import com.fragments.MyFragment
public class MyPagerAdapter extends FragmentPagerAdapter {
private String tabtitles[] = new String[] { "Info" };
private CustomOjbect object;
public MyPagerAdapter(FragmentManager fm, CustomOjbect object) {
super(fm);
this.object = object;
}
@Override
public Fragment getItem(int index) {
switch (index) {
case 0:
return new MyFragment(object);
}
return null;
}
@Override
public int getCount() {
return 1;
}
@Override
public CharSequence getPageTitle(int position) {
return tabtitles[position];
}
}
片段代码 [代码很大，因为其他代码只保留核心代码]
public class MyFragment extends Fragment implements OnClickListener {
/**
Variable declaration for widgets and views comes here
**/
public MyFragment(CustomObject object) {
this.object = object;
}
public MyFragment()
{
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
view = inflater.inflate(R.layout.fragment_layout,
container, false);
initializeUIComponents();
/**
...
..
rest of code
**/
return view;
}
private void initializeUIComponents() {
// ui views initialization
}
}
在视图寻呼机中，我调用带有争论的构造函数。为什么会失败？
【问题讨论】：
-
粘贴你调用构造函数的代码行
-
向我们展示片段的完整来源。
-
您可以从这里link获得更多有趣的信息
-
@Ugo 我所有活动都只有纵向
-
这与方向无关。这是关于重载的构造函数和非静态内部 Fragment 类。您可能将 Fragment 作为另一个类的内部类。在这种情况下，它应该是静态的。该问题的答案可能会告诉您更多信息。