我的活动包含两个片段（ Frag1 ， Frag2 ）。
在 Frag1 中，我有 EditText 。
在 Frag2 中，我有一个按钮和 TextView 。
我想要做的是，当我点击按钮时，我在EditText中键入的内容将显示在Textview中。这是我的代码，但它不起作用，因为每当我试图运行它时我的应用程序崩溃了：
Frag1：
public class Frag1 extends Fragment {
EditText edit1;
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.frag2, container, false);
edit1 = (EditText) getActivity().findViewById(R.id.edit_1);
String str = edit1.getText().toString();
Intent intent = new Intent(getActivity().getBaseContext(),
MainActivity.class);
intent.putExtra("message", str);
getActivity().startActivity(intent);
return v;
}
}
活动：
public class MainActivity extends FragmentActivity{
ViewPager viewPager = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
viewPager = (ViewPager) findViewById(R.id.pager);
FragmentManager fragmentManager = getSupportFragmentManager();
viewPager.setAdapter(new MyAdapter(fragmentManager));
Intent intent = getIntent();
String message = intent.getStringExtra("message");
Bundle bundle=new Bundle();
bundle.putString("message", message);
Frag2 fragobj=new Frag2();
fragobj.setArguments(bundle);
}
public class MyAdapter extends FragmentStatePagerAdapter {
public MyAdapter (FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int i) {
Fragment fragment = null;
if (i == 0)
{
fragment = new Frag1();
}
if (i == 1)
{
fragment = new Frag2();
}
return fragment;
}
@Override
public int getCount() {
return 2;
}
}
}
Frag2：
public class Frag2 extends Fragment implements OnClickListener {
Button button1;
TextView text1;
String strtext;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.frag2, container, false);
button1 = (Button) getActivity().findViewById(R.id.button1);
button1.setOnClickListener(this);
text1 = (TextView) getActivity().findViewById(R.id.text1);
strtext=getArguments().getString("message");
return v;
}
@Override
public void onClick(View arg0) {
text1.setText(strtext);
}
}
logcat的：
12-01 02:47:22.763: D/jdwp(4115): sendBufferedRequest : len=0x31
12-01 02:47:22.769: W/asset(4115): AssetManager-->addDefaultAssets CIP path not exsit!
12-01 02:47:23.061: V/PhoneWindow(4115): DecorView setVisiblity: visibility = 4
12-01 02:47:23.084: V/PhoneWindow(4115): DecorView setVisiblity: visibility = 0
12-01 02:47:23.160: D/AndroidRuntime(4115): Shutting down VM
12-01 02:47:23.160: W/dalvikvm(4115): threadid=1: thread exiting with uncaught exception (group=0x40d819a8)
12-01 02:47:23.178: E/AndroidRuntime(4115): FATAL EXCEPTION: main
12-01 02:47:23.178: E/AndroidRuntime(4115): java.lang.NullPointerException
12-01 02:47:23.178: E/AndroidRuntime(4115): at lmf.sample5.Frag1.onCreateView(Frag1.java:21)
12-01 02:47:23.178: E/AndroidRuntime(4115): at android.support.v4.app.Fragment.performCreateView(Fragment.java:1478)
12-01 02:47:23.178: E/AndroidRuntime(4115): at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:927)
12-01 02:47:23.178: E/AndroidRuntime(4115): at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1104)
12-01 02:47:23.178: E/AndroidRuntime(4115): at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:682)
12-01 02:47:23.178: E/AndroidRuntime(4115): at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1460)
12-01 02:47:23.178: E/AndroidRuntime(4115): at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:472)
12-01 02:47:23.178: E/AndroidRuntime(4115): at android.support.v4.app.FragmentStatePagerAdapter.finishUpdate(FragmentStatePagerAdapter.java:163)
12-01 02:47:23.178: E/AndroidRuntime(4115): at android.support.v4.view.ViewPager.populate(ViewPager.java:1068)
12-01 02:47:23.178: E/AndroidRuntime(4115): at android.support.v4.view.ViewPager.populate(ViewPager.java:914)
12-01 02:47:23.178: E/AndroidRuntime(4115): at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1436)
12-01 02:47:23.178: E/AndroidRuntime(4115): at android.view.View.measure(View.java:15635)
12-01 02:47:23.178: E/AndroidRuntime(4115): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4919)
12-01 02:47:23.178: E/AndroidRuntime(4115): at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
12-01 02:47:23.178: E/AndroidRuntime(4115): at android.view.View.measure(View.java:15635)
12-01 02:47:23.178: E/AndroidRuntime(4115): at android.widget.LinearLayout.measureVertical(LinearLayout.java:850)
12-01 02:47:23.178: E/AndroidRuntime(4115): at android.widget.LinearLayout.onMeasure(LinearLayout.java:588)
12-01 02:47:23.178: E/AndroidRuntime(4115): at android.view.View.measure(View.java:15635)
12-01 02:47:23.178: E/AndroidRuntime(4115): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4919)
12-01 02:47:23.178: E/AndroidRuntime(4115): at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
12-01 02:47:23.178: E/AndroidRuntime(4115): at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2200)
12-01 02:47:23.178: E/AndroidRuntime(4115): at android.view.View.measure(View.java:15635)
12-01 02:47:23.178: E/AndroidRuntime(4115): at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2165)
12-01 02:47:23.178: E/AndroidRuntime(4115): at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1249)
12-01 02:47:23.178: E/AndroidRuntime(4115): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1443)
12-01 02:47:23.178: E/AndroidRuntime(4115): at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1139)
12-01 02:47:23.178: E/AndroidRuntime(4115): at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4872)
12-01 02:47:23.178: E/AndroidRuntime(4115): at android.view.Choreographer$CallbackRecord.run(Choreographer.java:776)
12-01 02:47:23.178: E/AndroidRuntime(4115): at android.view.Choreographer.doCallbacks(Choreographer.java:579)
12-01 02:47:23.178: E/AndroidRuntime(4115): at android.view.Choreographer.doFrame(Choreographer.java:548)
12-01 02:47:23.178: E/AndroidRuntime(4115): at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:762)
12-01 02:47:23.178: E/AndroidRuntime(4115): at android.os.Handler.handleCallback(Handler.java:800)
12-01 02:47:23.178: E/AndroidRuntime(4115): at android.os.Handler.dispatchMessage(Handler.java:100)
12-01 02:47:23.178: E/AndroidRuntime(4115): at android.os.Looper.loop(Looper.java:194)
12-01 02:47:23.178: E/AndroidRuntime(4115): at android.app.ActivityThread.main(ActivityThread.java:5371)
12-01 02:47:23.178: E/AndroidRuntime(4115): at java.lang.reflect.Method.invokeNative(Native Method)
12-01 02:47:23.178: E/AndroidRuntime(4115): at java.lang.reflect.Method.invoke(Method.java:525)
12-01 02:47:23.178: E/AndroidRuntime(4115): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
12-01 02:47:23.178: E/AndroidRuntime(4115): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
12-01 02:47:23.178: E/AndroidRuntime(4115): at dalvik.system.NativeStart.main(Native Method)
答案 0 :(得分：2)
要访问片段内的元素，您需要膨胀的视图而不是父活动。例如
此
edit1 = (EditText) getActivity().findViewById(R.id.edit_1);
应更改为此
edit1 = (EditText) v.findViewById(R.id.edit_1);
编辑：
根据log cat，你现在在Frag 1第21行得到一个空指针异常。我认为这一行：
String str = edit1.getText().toString();
首次创建片段时，edit1中没有文本，其值为null，并且您尝试在空对象上调用toString（），这会导致空指针异常。你应该先检查它是否为null。例如：
String str =null;
if(edit1.getText()!==null)
str = edit1.getText().toString();
答案 1 :(得分：0)
您可以使用两个界面来完成。你的策略是这样的：
TestActivity持有Fragment1和Fragment2。
Fragment1有：
EditText etEditHere;
Fragment2有：
TextView tvFetchedValue;
Button btnGetValue;
您的动机是etEditHere fragment1，btnGetValue按Fragment2，etEditHere文字将显示在tvFetchedValue Fragment2 1}}。
这是解决方案：
你必须提醒一下，一个片段不能直接与另一个片段通信。但片段可以通过活动进行交流。
你必须创建2个接口，一个用于TestActivity，一个用于Fragment1。
Activity将实现此接口：
public interface IActivityTest {
public String getValueFromFragment1();
}
Fragment1 will implements this interface:
public interface IFragment1 {
public String getValueFromEditTextInFragment1();
}
此处TestActivity实施IActivityTest，它将采用getValue()方法。
此处，当按下btnGetValue时，它会以这种方式调用getValueFromEditTextInFragment1() TestActivity：
tvFetchedValue.setText(((IActivityTest)getActivity()).getValueFromFragment1());
在getValueFromFragment1()的{{1}}方法中，它会调用TestActivity的{{1}}。 getValueFromFragment1()会将editText值返回Fragment1。
Fragment1将返回TestActivity。
您的完整代码在此处：
TestActivity Layout：
TestActivityFragment1布局：
Fragment2Fragment1 Java文件：
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:baselineAligned="false"
android:orientation="vertical" >
<fragment
android:id="@+id/fragmentTwo"
android:name="YOUR_PACKAGE.Fragment2"
android:layout_width="fill_parent"
android:layout_height="200dp"/>
<fragment
android:id="@+id/fragmentOne"
android:layout_marginTop="10dp"
android:name="YOUR_PACKAGE.Fragment1"
android:layout_width="fill_parent"
android:layout_height="200dp" />
</LinearLayout>
Fragment2布局文件：
<FrameLayout 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="com.nuspay.uddiponmarketplace.fragments.Fragment1">
<EditText
android:id="@+id/etEditHere"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center"
android:textSize="20dp"
android:hint="Write Here"/>
</FrameLayout>
Fragment2 java文件：
public class Fragment1 extends Fragment implements IFragment1 {
EditText etEditHere;
public Fragment1() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view=inflater.inflate(R.layout.fragment_fragment1, container, false);
initView(view);
return view;
}
private void initView(View view) {
etEditHere= (EditText) view.findViewById(R.id.etEditHere);
}
@Override
public String getValueFromEditTextInFragment1() {
return etEditHere.getText().toString().trim();
}
}
最后，这是<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="com.nuspay.uddiponmarketplace.fragments.Fragment2"
android:orientation="vertical">
<!-- TODO: Update blank fragment layout -->
<TextView
android:id="@+id/tvFetchedValue"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="Value will come here"
android:gravity="center"
android:textSize="17dp"
android:padding="10dp"/>
<Button
android:id="@+id/btnGetValue"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Get Value From Fragment1"
android:gravity="center"
android:textStyle="bold"
android:textSize="17dp"
android:padding="10dp"/>
</LinearLayout>
public class Fragment2 extends Fragment {
TextView tvFetchedValue;
Button btnGetValue;
public Fragment2() {
// Required empty public constructor
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view=inflater.inflate(R.layout.fragment_fragment2, container, false);
initView(view);
return view;
}
private void initView(View view) {
tvFetchedValue= (TextView) view.findViewById(R.id.tvFetchedValue);
btnGetValue= (Button) view.findViewById(R.id.btnGetValue);
btnGetValue.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
tvFetchedValue.setText(((IActivityTest)getActivity()).getValueFromFragment1());
}
});
}
}
片段到活动通信答案是here
感谢和抱歉英语不好：）
答案 2 :(得分：0)
您对两个片段使用了相同的布局：R.layout.frag2
这是空指针。