Question

这是代码，它基本上是一个简单的菜单驱动的应用程序，我试图在片段内使用自定义字体，这是一个问题。我已经在一个活动中成功使用了这个字体，这个菜单活动启动了另一个活动，在这个活动中，这个片段被夸大了。我不确定这是否是导致问题的原因所以请帮帮我。

package com.cbs.CoronaTheCarnival;

    import android.app.Fragment;
    import android.graphics.Typeface;
    import android.os.Bundle;
    import android.view.View;
    import android.view.LayoutInflater;
    import android.view.ViewGroup;
    import android.widget.TextView;


    /**
     * Created by aditya on 2/4/14.
     */
    public class AboutFragment extends Fragment{

        View rootView;
        public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){
            View rootView = inflater.inflate(R.layout.fragment_about, container, false);
            initFonts();
            return rootView;

        }

         public void initFonts(){

            TextView tv_title = (TextView) rootView.findViewById(R.id.tv_about_title);
            Typeface changeFont = Typeface.createFromAsset(getActivity().getAssets(), "TRACK.OTF");
            tv_title.setTypeface(changeFont);
            TextView tv_theme = (TextView) rootView.findViewById(R.id.tv_about_theme);
            tv_theme.setTypeface(changeFont);

        }


    }

这是logcat，它说异常错误，我不知道为什么它不起作用，请帮助我，它杀了我和早上4:21。

02-06 04:19:41.534    3591-3591/com.cbs.CoronaTheCarnival E/AndroidRuntime﹕ FATAL EXCEPTION: main
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.cbs.CoronaTheCarnival/com.cbs.CoronaTheCarnival.HomeActivity}: java.lang.NullPointerException
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
            at android.app.ActivityThread.access$600(ActivityThread.java:141)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
            at android.os.Handler.dispatchMessage(Handler.java:99)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:5041)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
            at dalvik.system.NativeStart.main(Native Method)
     Caused by: java.lang.NullPointerException
            at com.cbs.CoronaTheCarnival.AboutFragment.initFonts(AboutFragment.java:27)
            at com.cbs.CoronaTheCarnival.AboutFragment.onCreateView(AboutFragment.java:20)
            at android.app.Fragment.performCreateView(Fragment.java:1695)
            at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:885)
            at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1057)
            at android.app.BackStackRecord.run(BackStackRecord.java:682)
            at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1435)
            at android.app.Activity.performStart(Activity.java:5113)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2153)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
            at android.app.ActivityThread.access$600(ActivityThread.java:141)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
            at android.os.Handler.dispatchMessage(Handler.java:99)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:5041)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
            at dalvik.system.NativeStart.main(Native Method)

Answer 1

您永远不会为成员rootView分配值。变化

public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){
    View rootView = inflater.inflate(R.layout.fragment_about, container, false);
    initFonts();
    return rootView;
}

到

public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){
    rootView = inflater.inflate(R.layout.fragment_about, container, false);
    initFonts();
    return rootView;
}

但实际上这可能会更好地写成：

public class AboutFragment extends Fragment {
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){
        View rootView = inflater.inflate(R.layout.fragment_about, container, false);
        initFonts(rootView);
        return rootView;
    }

    public void initFonts(final View rootView) {
        TextView title = (TextView) rootView.findViewById(R.id.tv_about_title);
        Typeface font = Typeface.createFromAsset(getActivity().getAssets(), "TRACK.OTF");
        title.setTypeface(font);
        TextView theme = (TextView) rootView.findViewById(R.id.tv_about_theme);
        theme.setTypeface(font);
    }
}

完全避开rootView类成员。

如果你没有null rootView中对onDestroyView的引用，那么当片段放在后面的堆栈上时，你的片段将保留在所有的视图内存中，甚至虽然在这一点上它没有任何意见。

Answer 2

在initFonts方法中，执行以下操作：

TextView tv_title = (TextView) rootView.findViewById(R.id.tv_about_title);

这里，rootView为null，因为它从未正确初始化。您似乎混淆了2个rootView变量：

View rootView; // this is one variable
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){
        View rootView = inflater.inflate(R.layout.fragment_about, container, false);
        // this is not the same rootView !
        // here, rootView != this.rootView
        initFonts();
        return rootView;
    }

public void initFonts(){
    TextView tv_title = (TextView) rootView.findViewById(R.id.tv_about_title);
    // this is like using this.rootView.findViewById
    // ...
}

initFonts方法无法看到onCreateView方法中的rootView，因此它将使用您在onCreateView上声明的视图，第一个视图从未正确初始化。要解决这个问题，您可以将initFonts的代码移回onCreateView，将视图作为initFonts方法的参数传递，或者在onCreateView中初始化变量，如下所示：

this.rootView = rootView;

Answer 3

在CoronaTheCarnival.java第27行放置一个断点。检查该行中使用的所有引用，以确定哪一个为null。

Answer 4

您在班级中声明rootView，然后在onCreateView方法中重新声明它，这可能会限制其范围，使您尝试在initFont中引用它失败。移除View

中rootView声明的onCreateView部分

在片段android中设置自定义字体时出现异常错误

4 个答案: