Java 无法从android中单击按钮时的片段加载意图

我有几个片段，在我的android应用程序中，片段加载很好，但我想通过点击按钮（按钮在其中一个片段上）来执行意图。下面是代码

MainActivity.java

public class MainActivity extends FragmentActivity{
ViewPager viewPager=null;
    Button button;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);
        viewPager= (ViewPager) findViewById(R.id.pager);
        button = (Button) findViewById(R.id.button);

        // Capture button clicks
        button.setOnClickListener(new OnClickListener() {
            public void onClick(View arg0) {

                // Start NewActivity.class
                Intent myIntent = new Intent(MainActivity.this,eventload.class);
                startActivity(myIntent);
            }
        });
        FragmentManager fragmentManager=getSupportFragmentManager();
        viewPager.setAdapter(new MyAdapter(fragmentManager));
    }
}
class MyAdapter extends FragmentPagerAdapter
{
    public MyAdapter(FragmentManager fm) {
        super(fm);
        // TODO Auto-generated constructor stub
    }
    @Override
    public Fragment getItem(int i) {
        Fragment fragment = null;
        if (i==0)
        {
            fragment = new FragmentA();
        }
        if (i==1)
        {
            fragment = new FragmentB();
        }
        if (i==2)
        {
            fragment = new FragmentC();
        }


        return fragment;
    }

    @Override
    public int getCount() {

        return 3;
    }
    @Override
    public CharSequence getPageTitle(int position) {
        String title = new String();
        if (position==0)
        {
            return "Technical";
        }
        if (position==1)
        {
            return "Cultural";
        }
        if (position==2)
        {
            return "Sports";
        }


        return super.getPageTitle(position);
    }

}

下面是eventload类

public class eventload extends Activity {

    Button button;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.load);
    }

}

Load.xml只有一个单选按钮

这是舱单

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.layouts"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="21" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity android:name=".MainActivity"></activity>
        <activity android:name=".eventload"></activity>
        <activity
            android:name=".SplashScreen"
            android:label="@string/app_name" >


            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

我在舱单上提到了主要活动

下面是activity main.xml

<android.support.v4.view.ViewPager xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"


    android:id="@+id/pager"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity" 
    android:background="@drawable/ic_launcher">
   <android.support.v4.view.PagerTitleStrip
        android:id="@+id/title"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="top"
        android:background="#33b5e5"
        android:paddingBottom="4dp"
        android:paddingTop="4dp"
        android:textColor="#fff" />


</android.support.v4.view.ViewPager>

---

您告诉button在片段上，但您正在活动中实例化该按钮，而该按钮不在活动中。所以它得到了NullPointerException。在存在按钮的片段中实例化按钮

更新1 像这样更改片段onCreateView（）方法

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

    View view = inflater.inflate(R.layout.frag4, container, false);
    Button button = (Button) view.findViewById(R.id.button);

    // Capture button clicks
    button.setOnClickListener(new OnClickListener() {
        public void onClick(View arg0) {

            // Start NewActivity.class
            Intent myIntent = new Intent(getActivity(), eventload.class);
            startActivity(myIntent);
        }
    });

    return view

---

将frag4的代码更改如下：

     public class FragmentC  extends Fragment{
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
               View v = inflater.inflate(R.layout.frag4, container, false);
    // here v is the View you inflated from frag4.xml
    Button button = (Button) v.findViewById(R.id.button);

    // Capture button clicks
    button.setOnClickListener(new OnClickListener() {
        public void onClick(View arg0) {

            // Start NewActivity.class
            Intent myIntent = new Intent(getActivity(),eventload.class);
            startActivity(myIntent);
        }
    });
    return v;
    }
}

---

创建意图对象时，将

getApplicationContext（）

作为中的第一个参数传递

现在，您的

按钮.setOnClickListener（）

应该如下所示

button.setOnClickListener(new OnClickListener() {
        public void onClick(View arg0) {

            // Start NewActivity.class
            Intent myIntent = new Intent(getApplicationContext(),eventload.class);
            startActivity(myIntent);
        }
    });

---

按钮在哪里

按钮？显示您的活动\u main.xml。问题在您的活动\u main.xml中。@prosper，按钮在frag4中。xml@penta你应该在布局中使用ViewPager，按钮也应该在同一布局中，然后它就会工作。如果我尝试按照你说的做，它会给出错误，你能在这里粘贴正确的代码吗编辑了我的问题你可以在这里看到它这次加载了应用程序，但是当我看到那个片段时它崩溃了，很抱歉，我无法理解哪个是我的视图，我提到了我的frag4.xml，你能看到哪个是我的视图并在这里告诉我吗（R.layout.frag4，容器，错误）；非常感谢，修复了它

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

    View view = inflater.inflate(R.layout.frag4, container, false);
    Button button = (Button) view.findViewById(R.id.button);

    // Capture button clicks
    button.setOnClickListener(new OnClickListener() {
        public void onClick(View arg0) {

            // Start NewActivity.class
            Intent myIntent = new Intent(getActivity(), eventload.class);
            startActivity(myIntent);
        }
    });

    return view

     public class FragmentC  extends Fragment{
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
               View v = inflater.inflate(R.layout.frag4, container, false);
    // here v is the View you inflated from frag4.xml
    Button button = (Button) v.findViewById(R.id.button);

    // Capture button clicks
    button.setOnClickListener(new OnClickListener() {
        public void onClick(View arg0) {

            // Start NewActivity.class
            Intent myIntent = new Intent(getActivity(),eventload.class);
            startActivity(myIntent);
        }
    });
    return v;
    }
}

button.setOnClickListener(new OnClickListener() {
        public void onClick(View arg0) {

            // Start NewActivity.class
            Intent myIntent = new Intent(getApplicationContext(),eventload.class);
            startActivity(myIntent);
        }
    });