Question

当我尝试使用ImageButton的setOnClickListener时，我收到了java.lang.NullPointerException，whisch是行的项目：

public class FragmentTab1 extends SherlockFragment {
ListView list;
LazyAdapter adapter;
ImageButton ib;
Fragment1 frag1;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)        {
    return inflater.inflate(R.layout.fragmenttab1, container, false);
}

@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
    list = (ListView) view.findViewById(android.R.id.list);
    final EditText editText = (EditText)view.findViewById(R.id.editText);
    Button buttFind = (Button)view.findViewById(R.id.buttFind);
    buttFind.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            if (editText.getText().toString() != null){
                final String url = strBldr(editText.getText().toString());
                new Thread(new Runnable() {
                    @Override
                    public void run() {
                        Parser parser = null;
                        try {
                            parser = new Parser(doRequest(url));
                        } catch (Exception e) {
                            e.printStackTrace();
                        }
                        mSource = parser.getSource();
                        Message msg = mHandler.obtainMessage();
                        mHandler.sendMessage(msg);
                    }
                }).start();
            }
        }
    });
    adapter = new LazyAdapter(getActivity(), mSource);
    list.setAdapter(adapter);                // all is OK
    ib = (ImageButton)list.findViewById(android.R.id.icon);
    ib.setOnClickListener(new View.OnClickListener() {                //here error
        @Override
        public void onClick(View view) {
            //
        }
    });
}

我还尝试了getActivity（）。finViewById，view.finViewById，但结果相同。这是xml的行：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal" >

<ImageButton
    android:id="@android:id/icon""
    android:layout_width="50dp"
    android:layout_height="50dp"
    android:layout_gravity="left|top"
    android:layout_marginLeft="10dp"
    android:layout_marginTop="10dp" />

<TextView
    android:id="@+id/title1"
    android:text="qweqwrqw"
    android:layout_width="200dp"
    android:layout_height="100dp"

    android:paddingLeft="15dp"
    android:textSize="15sp"
    android:layout_alignParentTop="true"
    android:layout_toRightOf="@+id/imageButton1"
    android:layout_toEndOf="@+id/imageButton1"

    android:layout_alignBottom="@+id/imageButton1" />

<CheckBox
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Save to database"
    android:id="@+id/checkBox1"
    android:layout_below="@+id/imageButton1"
    android:layout_alignParentRight="true"
    android:layout_alignParentEnd="true" />

有人可以遏制我，我做错了什么？

EDIT 对不起，我在FragmentTab1中发布了错误的示例ID。我在FragmentTab1中指出：ib =（ImageButton）list.findViewById（android.R.id.icon）和xml android：id =＆＃34; @android：id / icon＆＃34;，但崩溃时出现错误java.lang.NullPointerException 举个例子，引用日志：

10-21 17:17:26.672    1730-1730/com.tim_kriuchkov.task E/AndroidRuntime﹕ FATAL EXCEPTION: main
java.lang.NullPointerException
        at com.tim_kriuchkov.task.FragmentTab1.onCreateView(FragmentTab1.java:98)
        at android.support.v4.app.Fragment.performCreateView(Fragment.java:1504)
        at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:942)
        at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1121)
        at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:682)
        at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1484)
        at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:482)
        at android.support.v4.app.FragmentStatePagerAdapter.finishUpdate(FragmentStatePagerAdapter.java:163)
        at android.support.v4.view.ViewPager.populate(ViewPager.java:1073)
        at android.support.v4.view.ViewPager.populate(ViewPager.java:919)
        at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1441)
        at android.view.View.measure(View.java:12723)
        at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:594)
        at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:376)
        at android.view.View.measure(View.java:12723)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4698)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:293)
        at android.view.View.measure(View.java:12723)
        at android.widget.LinearLayout.measureVertical(LinearLayout.java:812)
        at android.widget.LinearLayout.onMeasure(LinearLayout.java:553)
        at android.view.View.measure(View.java:12723)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4698)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:293)
        at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2092)
        at android.view.View.measure(View.java:12723)
        at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1064)
        at android.view.ViewRootImpl.handleMessage(ViewRootImpl.java:2442)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:137)
        at android.app.ActivityThread.main(ActivityThread.java:4424)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:511)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
        at dalvik.system.NativeStart.main(Native Method)

Answer 1

更改ib = (ImageButton)list.findViewById(android.R.id.icon); 到ib = (ImageButton)list.findViewById(android.R.id.imageButton1); Radoslav找到你的错误：

以调试模式启动应用程序以查看更多详细信息。

Answer 2

你显然要复制一些你不理解的代码。

我看到的其中一个错误就在

行

   ib = (ImageButton)list.findViewById(android.R.id.icon);

你的ImageButton id是“imageButton1”而不是“android.R.id.icon”

Answer 3

这一行错了：

list.findViewById(android.R.id.icon);

您应该使用：

list.findViewById(android.R.id.imageButton1);

SherlockFragment ListView得到

3 个答案: