我收到错误“Unreachable statement"返回安卓 [英] I get the error "Unreachable statement" return in android

问题描述

为什么我会收到第 92 行是一条无法访问的语句的错误消息?错误在这一行:

Why do I get the error that line 92 is an unreachable statement? The error is in this line:

final RadioButton r1 = (RadioButton) getView().findViewById(R.id.radio1);

代码:

public class TabFragmentA extends Fragment {


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {

        if (container == null) {
            return null;
        }

        return (RelativeLayout) inflater.inflate(R.layout.tab_layout_a, container, false);


        final RadioButton r1 = (RadioButton) getView().findViewById(R.id.radio1);  //the error is here
        final RadioButton r2 = (RadioButton) getView().findViewById(R.id.radio2);

        final ImageView iv1 = (ImageView) getView().findViewById(R.id.iv1); 
        final ImageView iv2 = (ImageView) getView().findViewById(R.id.iv2);

        iv1.setVisibility(View.INVISIBLE);
        iv2.setVisibility(View.INVISIBLE);

        r1.setOnCheckedChangeListener(new OnCheckedChangeListener() {

            public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                // TODO Auto-generated method stub
                if(r1.isChecked())
                {
                    r2.setChecked(false);
                    iv2.setVisibility(View.INVISIBLE);
                    iv1.setVisibility(View.VISIBLE);
                }
            }
        });

        r2.setOnCheckedChangeListener(new OnCheckedChangeListener() {

            public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                // TODO Auto-generated method stub
                if(r2.isChecked())
                {
                    r1.setChecked(false);
                    iv1.setVisibility(View.INVISIBLE);
                    iv2.setVisibility(View.VISIBLE);
                }
            }
        });
    }
}

Logcat 错误:

01-23 02:43:31.082    1903-1903/br.com.eddboytools.PreDim E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: br.com.eddboytools.PreDim, PID: 1903
    java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.View.findViewById(int)' on a null object reference
            at br.com.eddboytools.PreDim.TabFragmentA.onCreateView(TabFragmentA.java:29)
            at android.support.v4.app.Fragment.performCreateView(Fragment.java:1478)
            at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:927)
            at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1104)
            at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:682)
            at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1460)
            at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:472)
            at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:141)
            at android.support.v4.view.ViewPager.populate(ViewPager.java:1068)
            at android.support.v4.view.ViewPager.populate(ViewPager.java:914)
            at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1436)
            at android.view.View.measure(View.java:17430)
            at android.widget.LinearLayout.measureVertical(LinearLayout.java:875)
            at android.widget.LinearLayout.onMeasure(LinearLayout.java:613)
            at android.view.View.measure(View.java:17430)
            at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463)
            at android.widget.FrameLayout.onMeasure(FrameLayout.java:430)
            at android.view.View.measure(View.java:17430)
            at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463)
            at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436)
            at android.widget.LinearLayout.measureVertical(LinearLayout.java:722)
            at android.widget.LinearLayout.onMeasure(LinearLayout.java:613)
            at android.view.View.measure(View.java:17430)
            at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463)
            at android.widget.FrameLayout.onMeasure(FrameLayout.java:430)
            at android.view.View.measure(View.java:17430)
            at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463)
            at com.android.internal.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:447)
            at android.view.View.measure(View.java:17430)
            at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463)
            at android.widget.FrameLayout.onMeasure(FrameLayout.java:430)
            at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2560)
            at android.view.View.measure(View.java:17430)
            at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2001)
            at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1166)
            at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1372)
            at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1054)
            at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5779)
            at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767)
            at android.view.Choreographer.doCallbacks(Choreographer.java:580)
            at android.view.Choreographer.doFrame(Choreographer.java:550)
            at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:753)
            at android.os.Handler.handleCallback(Handler.java:739)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
01-23 02:43:31.094    1903-1915/br.com.eddboytools.PreDim I/art﹕ Background partial concurrent mark sweep GC freed 261(11KB) AllocSpace objects, 0(0B) LOS objects, 27% free, 1328KB/1840KB, paused 20.856ms total 51.174ms

推荐答案

我们不会将 return 语句置于任何其他语句之上，除非 return 在任何条件语句之下.如果我们这样做，那么下面的所有语句将永远不会被执行(意味着它在所有情况下都将变得无法访问)，从而导致您遇到的错误.

We don't put return statement above any other statement unless that return is under any conditional statement. If we do that then all the statements below that would never get executed (means it would become unreachable under all circumstances) which causes the error you are getting.

这样做

public class TabFragmentA extends Fragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {

    RelativeLayout rootView = (RelativeLayout) inflater.inflate(R.layout.tab_layout_a, container, false);


    final RadioButton r1 = (RadioButton) rootView.findViewById(R.id.radio1);
    final RadioButton r2 = (RadioButton) rootView.findViewById(R.id.radio2);

    final ImageView iv1 = (ImageView) rootView.findViewById(R.id.iv1);
    final ImageView iv2 = (ImageView) rootView.findViewById(R.id.iv2);

    iv1.setVisibility(View.INVISIBLE);
    iv2.setVisibility(View.INVISIBLE);

    r1.setOnCheckedChangeListener(new OnCheckedChangeListener() {

        public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
            // TODO Auto-generated method stub
            if(r1.isChecked())
            {
                r2.setChecked(false);
                iv2.setVisibility(View.INVISIBLE);
                iv1.setVisibility(View.VISIBLE);
            }
        }
    });

    r2.setOnCheckedChangeListener(new OnCheckedChangeListener() {

        public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
            // TODO Auto-generated method stub
            if(r2.isChecked())
            {
                r1.setChecked(false);
                iv1.setVisibility(View.INVISIBLE);
                iv2.setVisibility(View.VISIBLE);
            }
        }
    });
return rootView;
}
}

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