使用setOnClickListener进行片段崩溃

Question

我有扩展BaseActivity的不同活动。当我点击按钮时：

public class Item1Activity extends BaseActivity { 
Button button1; 
@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    button1 = (Button) findViewById(R.id.button1); 

    /** 
    * We will not use setContentView in this activity 
    * Rather than we will use layout inflater to add view in FrameLayout of our base activity layout*/ 

    /** 
    * Adding our layout to parent class frame layout. 
    */ 
    getLayoutInflater().inflate(R.layout.activity_main, frameLayout); 
    button1.setOnClickListener(new View.OnClickListener() { 
     public void onClick(View view) { 
      Intent intent = new Intent(
        android.content.Intent.ACTION_VIEW, 
        Uri.parse("http://maps.google.com/maps?daddr=46.0796808,13.2393894,17z")); 
      startActivity(intent); 
     } 
    }); 

当我启动应用程序时，它的崩溃与NullPointerException。 这是日志：

12-09 08:30:44.305: E/AndroidRuntime(740): Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference 
12-09 08:30:44.305: E/AndroidRuntime(740): at com.navigation.drawer.activity.Item1Activity.onCreate(Item1Activity.java:30) 

我的基本活动是：

public class BaseActivity extends Activity { 

/** 
* Frame layout: Which is going to be used as parent layout for child activity layout. 
* This layout is protected so that child activity can access this 
* */ 
protected FrameLayout frameLayout; 

/** 
* ListView to add navigation drawer item in it. 
* We have made it protected to access it in child class. We will just use it in child class to make item selected according to activity opened. 
*/ 

protected ListView mDrawerList; 

/** 
* List item array for navigation drawer items. 
* */ 
protected String[] listArray = { "Item 1", "Item 2", "Item 3", "Item 4", "Item 5" }; 

/** 
* Static variable for selected item position. Which can be used in child activity to know which item is selected from the list. 
* */ 
protected static int position; 

/** 
* This flag is used just to check that launcher activity is called first time 
* so that we can open appropriate Activity on launch and make list item position selected accordingly.  
* */ 
private static boolean isLaunch = true; 

/** 
* Base layout node of this Activity.  
* */ 
private DrawerLayout mDrawerLayout; 

/** 
* Drawer listner class for drawer open, close etc. 
*/ 
private ActionBarDrawerToggle actionBarDrawerToggle; 


@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.navigation_drawer_base_layout); 

    frameLayout = (FrameLayout)findViewById(R.id.content_frame); 
    mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout); 
    mDrawerList = (ListView) findViewById(R.id.left_drawer); 


    mDrawerList.setAdapter(new ArrayAdapter<String>(this,  R.layout.drawer_list_item, listArray)); 
     mDrawerList.setOnItemClickListener(new OnItemClickListener() { 

     @Override 
     public void onItemClick(AdapterView<?> parent, View view, 
       int position, long id) { 

      openActivity(position); 
     } 
    }); 

    // enable ActionBar app icon to behave as action to toggle nav drawer 
    getActionBar().setDisplayHomeAsUpEnabled(true); 
    getActionBar().setHomeButtonEnabled(true); 

    // ActionBarDrawerToggle ties together the the proper interactions between the sliding drawer and the action bar app icon 
    actionBarDrawerToggle = new ActionBarDrawerToggle(
      this,      /* host Activity */ 
      mDrawerLayout,    /* DrawerLayout object */ 
      R.drawable.ic_launcher,  /* nav drawer image to replace 'Up' caret */ 
      R.string.open_drawer,  /* "open drawer" description for accessibility */ 
      R.string.close_drawer)  /* "close drawer" description for accessibility */ 
    { 
     @Override 
     public void onDrawerClosed(View drawerView) { 
      getActionBar().setTitle(listArray[position]); 
      invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu() 
      super.onDrawerClosed(drawerView); 
     } 

     @Override 
     public void onDrawerOpened(View drawerView) { 
      getActionBar().setTitle(getString(R.string.app_name)); 
      invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu() 
      super.onDrawerOpened(drawerView); 
     } 

     @Override 
     public void onDrawerSlide(View drawerView, float slideOffset) { 
      super.onDrawerSlide(drawerView, slideOffset); 
     } 

     @Override 
     public void onDrawerStateChanged(int newState) { 
      super.onDrawerStateChanged(newState); 
     } 
    }; 
    mDrawerLayout.setDrawerListener(actionBarDrawerToggle); 


    /** 
    * As we are calling BaseActivity from manifest file and this base activity is intended just to add navigation drawer in our app. 
    * We have to open some activity with layout on launch. So we are checking if this BaseActivity is called first time then we are opening our first activity. 
    * */ 
    if(isLaunch){ 
     /** 
      *Setting this flag false so that next time it will not open our first activity. 
      *We have to use this flag because we are using this BaseActivity as parent activity to our other activity. 
      *In this case this base activity will always be call when any child activity will launch. 
      */ 
     isLaunch = false; 
     openActivity(0); 
    } 
} 

/** 
* @param position 
* 
* Launching activity when any list item is clicked. 
*/ 
protected void openActivity(int position) { 

    /** 
    * We can set title & itemChecked here but as this BaseActivity is parent for other activity, 
    * So whenever any activity is going to launch this BaseActivity is also going to be called and 
    * it will reset this value because of initialization in onCreate method. 
    * So that we are setting this in child activity.  
    */ 
    mDrawerList.setItemChecked(position, true); 
    setTitle(listArray[position]); 
    mDrawerLayout.closeDrawer(mDrawerList); 
    BaseActivity.position = position; 

    switch (position) { 
    case 0: 
     startActivity(new Intent(this, Item1Activity.class)); 
     break; 
    case 1: 
     startActivity(new Intent(this, Item2Activity.class)); 
     break; 
    case 2: 
     startActivity(new Intent(this, Item3Activity.class)); 
     break; 
    case 3: 
     startActivity(new Intent(this, Item4Activity.class)); 
     break; 
    case 4: 
     startActivity(new Intent(this, Item5Activity.class)); 
     break; 

    default: 
     break; 
    } 

    Toast.makeText(this, "Selected Item Position::"+position, Toast.LENGTH_LONG).show(); 
} 

@Override 
public boolean onCreateOptionsMenu(Menu menu) { 

    getMenuInflater().inflate(R.menu.main, menu); 
    return super.onCreateOptionsMenu(menu); 
} 

@Override 
public boolean onOptionsItemSelected(MenuItem item) { 

    // The action bar home/up action should open or close the drawer. 
    // ActionBarDrawerToggle will take care of this. 
    if (actionBarDrawerToggle.onOptionsItemSelected(item)) { 
     return true; 
    } 

    switch (item.getItemId()) { 
    case R.id.action_settings: 
     return true; 

    default: 
     return super.onOptionsItemSelected(item); 
    } 
} 

/* Called whenever we call invalidateOptionsMenu() */ 
@Override 
public boolean onPrepareOptionsMenu(Menu menu) { 
    // If the nav drawer is open, hide action items related to the content view 
    boolean drawerOpen = mDrawerLayout.isDrawerOpen(mDrawerList); 
    menu.findItem(R.id.action_settings).setVisible(!drawerOpen); 
    return super.onPrepareOptionsMenu(menu); 
} 

/* We can override onBackPressed method to toggle navigation drawer*/ 
@Override 
public void onBackPressed() { 
    if(mDrawerLayout.isDrawerOpen(mDrawerList)){ 
     mDrawerLayout.closeDrawer(mDrawerList); 
    }else { 
     mDrawerLayout.openDrawer(mDrawerList); 
    } 
} 
} 

Answer 1

在哪里按钮定义？如果它在R.layout.activity_main那么你应该先膨胀，然后尝试找到按钮。更改代码：

第一：

getLayoutInflater().inflate(R.layout.activity_main, frameLayout); 

二：

button1 = (Button) findViewById(R.id.button1); 

这应该做的伎俩。