片段活动片段通讯

Question

我有一个带有两个片段（Frag1、Frag2）的Activity。

在 Frag1 中，我有一个 EditText。

在 Frag2 中，我有一个 Button 和 TextView。

我想要做的是，当我单击按钮时，我在 EditText 中键入的任何内容都会出现在 Textview 中。这是我的代码，但它不起作用，因为每当我尝试运行它时我的应用程序就会崩溃：

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：

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)

Answer 1

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

这个

    edit1 = (EditText) getActivity().findViewById(R.id.edit_1); 

应该改成这个

    edit1 = (EditText) v.findViewById(R.id.edit_1); 

编辑：

根据日志 cat 现在你在 Frag 1 第 21 行得到一个空指针异常。我认为它是这一行：

   String str = edit1.getText().toString();

当第一次创建片段时，edit1 中没有文本，它的值为空，您试图在空对象上调用 toString()，这会导致空指针异常。您应该首先检查它是否为空。例如：

    String str =null;
    if(edit1.getText()!==null)
        str = edit1.getText().toString();

Answer 2

您对两个片段使用了相同的布局：R.layout.frag2

这是给空指针。

Answer 3

您可以使用两个接口来完成。你的策略是这样的：

TestActivity 持有Fragment1 和Fragment2。

Fragment1 有：

EditText etEditHere;

Fragment2 有：

TextView tvFetchedValue;
    Button btnGetValue;

你的动机写在fragment1的etEditHere，按Fragment2的btnGetValue，etEditHere的文字将显示在tvFetchedValue的Fragment2。

这里是解决方案：

您必须提醒，一个片段不能直接与另一个片段通信。但是片段可以通过活动进行通信。

您必须创建 2 个接口，一个用于 TestActivity，一个用于 Fragment1。

Activity 会实现这个接口：

    public interface IActivityTest {
    public String getValueFromFragment1();
}

Fragment1 will implements this interface:

    public interface IFragment1 {
    public String getValueFromEditTextInFragment1();
}

在这里，TestActivity 实现了IActivityTest，它将具有getValue() 方法。

这里，当btnGetValue被按下时，它将使用这种方式调用TestActivity的getValueFromEditTextInFragment1()：

tvFetchedValue.setText(((IActivityTest)getActivity()).getValueFromFragment1());

在TestActivity 的getValueFromFragment1() 方法中，它将调用Fragment1 的getValueFromFragment1()。 Fragment1 会将 editText 值返回给 TestActivity 。 TestActivity 将返回到 Fragment2。

您的完整代码在这里：

TestActivity 布局：

<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>

Fragment1 布局：

<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>

Fragment1 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();
}
}

Fragment2 布局文件：

<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>

Fragment2 java 文件：

 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());
                }
            });
        }

    }

最后，这是TestActivity

public class TestActivity extends AppCompatActivity implements IActivityTest {

    Fragment1 fragment1;
    Fragment2 fragment2;

    @Override
    public void onCreate(Bundle iclic) {
        super.onCreate(iclic);
        setContentView(R.layout.activity_test);
        initViews();
    }

    private void initViews() {
        fragment1=new Fragment1();
        fragment2=new Fragment2();

        FragmentTransaction transaction =
                getSupportFragmentManager().beginTransaction();

        transaction.add(R.id.fragmentOne, fragment1);
        transaction.add(R.id.fragmentTwo, fragment2);
        transaction.commit();


    }

    @Override
public String getValueFromFragment1() {

    return fragment1.getValueFromEditTextInFragment1();
}
}

Fragment to Activity Communication 答案是here

感谢和抱歉英语不好:)