我的按钮丢失了什么?

时间:2013-09-05 15:28:54

标签: java android button android-fragments nullpointerexception

好的,所以我在键盘上敲打了大约2天。 当我运行程序时,它强制关闭,log cat告诉我一个空指针。 当我将按钮放在评论中时,程序将打开。 (更新) 现在它运行没有nullpointer但onclick()不起作用。 也许这是我如何给按钮充气的问题。

好的,所以我编辑了按钮,现在看起来像这样,

Button b;
    View v1 = getLayoutInflater().inflate(R.layout.current, null);
    b = (Button) v1.findViewById(R.id.okbutton);

    b.setOnClickListener(new OnClickListener() {

            public void onClick(View v) {
            result.setText("Test");
            }

            });

但是,我认为问题可能出在我如何连接主xml中的T​​abs。

所以这是我的代码的全部内容。

import java.util.*;
import android.app.*;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.view.*;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;


public class MainActivity extends FragmentActivity implements
    ActionBar.TabListener {

/**
 * The {@link android.support.v4.view.PagerAdapter} that will provide
 * fragments for each of the sections. We use a
 * {@link android.support.v4.app.FragmentPagerAdapter} derivative, which
 * will keep every loaded fragment in memory. If this becomes too memory
 * intensive, it may be best to switch to a
 * {@link android.support.v4.app.FragmentStatePagerAdapter}.
 */
SectionsPagerAdapter mSectionsPagerAdapter;

/**
 * The {@link ViewPager} that will host the section contents.
 */
ViewPager mViewPager;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    // Set up the action bar.
    final ActionBar actionBar = getActionBar();
    final TextView result = (TextView) findViewById(R.id.TextView);
    //final GameEventHandler object = new GameEventHandler();
    actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
    // Create the adapter that will return a fragment for each of the three
    // primary sections of the app.
    mSectionsPagerAdapter = new SectionsPagerAdapter(
            getSupportFragmentManager());

    // Set up the ViewPager with the sections adapter.
    mViewPager = (ViewPager) findViewById(R.id.pager);
    mViewPager.setAdapter(mSectionsPagerAdapter);

    // When swiping between different sections, select the corresponding
    // tab. We can also use ActionBar.Tab#select() to do this if we have
    // a reference to the Tab.
    mViewPager
            .setOnPageChangeListener(new 
ViewPager.SimpleOnPageChangeListener() {
                @Override
                public void onPageSelected(int position) {

    actionBar.setSelectedNavigationItem(position);
                }
            });


    // For each of the sections in the app, add a tab to the action bar.
    for (int i = 0; i < mSectionsPagerAdapter.getCount(); i++) {
        // Create a tab with text corresponding to the page title defined by
        // the adapter. Also specify this Activity object, which implements
        // the TabListener interface, as the callback (listener) for when
        // this tab is selected.
        actionBar.addTab(actionBar.newTab()
                .setText(mSectionsPagerAdapter.getPageTitle(i))
                .setTabListener(this));

    }
Button b;
    View v1 = getLayoutInflater().inflate(R.layout.current, null);
    b = (Button) v1.findViewById(R.id.okbutton);

    b.setOnClickListener(new OnClickListener() {

            public void onClick(View v) {
            result.setText("Test");
            }

            });
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

@Override
public void onTabSelected(ActionBar.Tab tab,
        FragmentTransaction fragmentTransaction) {
    // When the given tab is selected, switch to the corresponding page in
    // the ViewPager.
    mViewPager.setCurrentItem(tab.getPosition());
}

@Override
public void onTabUnselected(ActionBar.Tab tab,
        FragmentTransaction fragmentTransaction) {
}

@Override
public void onTabReselected(ActionBar.Tab tab,
        FragmentTransaction fragmentTransaction) {
}

/**
 * A {@link FragmentPagerAdapter} that returns a fragment corresponding to
 * one of the sections/tabs/pages.
 */
public class SectionsPagerAdapter extends FragmentPagerAdapter {

    public SectionsPagerAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getItem(int position) {
        // getItem is called to instantiate the fragment for the given page.
        // Return a DummySectionFragment (defined as a static inner class
        // below) with the page number as its lone argument.
        Fragment fragment = new DummySectionFragment();
        Bundle args = new Bundle();
        args.putInt(DummySectionFragment.ARG_SECTION_NUMBER, position + 1);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public int getCount() {
        // Show 4 total pages.
        return 4;
    }

    @Override
    public CharSequence getPageTitle(int position) {
        Locale l = Locale.getDefault();
        switch (position) {
        case 0:
            return getString(R.string.title_section1).toUpperCase(l);
        case 1:
            return getString(R.string.title_section2).toUpperCase(l);
        case 2:
            return getString(R.string.title_section3).toUpperCase(l);
        case 3:
            return getString(R.string.title_section4).toUpperCase(l);
        }
        return null;
    }
}

/**
 * A dummy fragment representing a section of the app, but that simply
 * displays dummy text.
 */
public static class DummySectionFragment extends Fragment {
    /**
     * The fragment argument representing the section number for this
     * fragment.
     */
    public static final String ARG_SECTION_NUMBER = "section_number";

    public DummySectionFragment() {
    }

    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.current,
                container, false);
        TextView dummyTextView = (TextView) rootView
                .findViewById(R.id.textView1);
        dummyTextView.setText(Integer.toString(getArguments().getInt(
                ARG_SECTION_NUMBER)));

        if(dummyTextView.getText().equals("1") ){

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

        }
        if(dummyTextView.getText().equals("2")){
            rootView = inflater.inflate(R.layout.stats,
                container, false);
        }
        if(dummyTextView.getText().equals("3")){
            rootView = inflater.inflate(R.layout.inventory,
                container, false);
        }
        if(dummyTextView.getText().equals("4")){
            rootView = inflater.inflate(R.layout.options,
                container, false);
        }

        return rootView;
    }
}

}

,这是包含按钮的xml的xml;

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >

<RelativeLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:gravity="center_vertical" >

    <Button
        android:id="@+id/okbutton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/Yesbutton"
        android:layout_alignBottom="@+id/Yesbutton"
        android:layout_alignLeft="@+id/RollButton"
        android:text="ok" />

    <Button
        android:id="@+id/nobutton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/RollButton"
        android:layout_toRightOf="@+id/okbutton"
        android:text="no" />

    <Button
        android:id="@+id/Yesbutton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_above="@+id/textView1"
        android:layout_toLeftOf="@+id/okbutton"
        android:text="Yes" />

    <Button
        android:id="@+id/RollButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_above="@+id/okbutton"
        android:layout_centerHorizontal="true"
        android:text="Roll" />

    <TextView
        android:id="@+id/RollResult"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_above="@+id/RollButton"
        android:layout_centerHorizontal="true"
        android:text="0"
        android:textAppearance="?android:attr/textAppearanceLarge" />

    <TextView
        android:id="@+id/text2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_above="@+id/RollButton"
        android:layout_toLeftOf="@+id/RollResult"
        android:text="Current Roll:"
        android:textAppearance="?android:attr/textAppearanceLarge" />

    <TextView
        android:id="@+id/TextView"
        android:layout_width="200dp"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
        android:text="Welcome to the dungeon! press ok to start!"
        android:textAppearance="?android:attr/textAppearanceLarge" />

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_alignParentRight="true"
        android:text="1"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:textSize="1px" />

</RelativeLayout>

</LinearLayout>

对不起,如果我不够具体,这是我第一次不得不寻求帮助。

1 个答案:

答案 0 :(得分:0)

如果您这样做 - 您无法从其中一个片段中引用按钮,直到它被充气为止。即如果按钮在R.layout.current中定义,则会因为在调用setOnClickListener时没有按钮而崩溃。一旦确定片段膨胀,就需要稍后调用它。

(我会把它作为评论,但我还没有发表评论,因为我没有足够的代表)