我刚刚开始进行android开发。 我的主屏幕上有一个按钮，我想用拨打号码打开拨号器，但出于某种原因，当我去点击聆听时，应用程序崩溃了。
我可以取出点击监听器，应用程序打开正常。 我已经在清单中设置了用户权限，所以不能这样吗？
任何帮助都将不胜感激。
主要Activity.java
info.androidhive.slidingmenu;
import info.androidhive.slidingmenu.adapter.NavDrawerListAdapter;
import info.androidhive.slidingmenu.model.NavDrawerItem;
import java.util.ArrayList;
import android.app.Activity;
import android.app.Fragment;
import android.app.FragmentManager;
import android.content.Intent;
import android.content.res.Configuration;
import android.content.res.TypedArray;
import android.net.Uri;
import android.os.Bundle;
import android.support.v4.app.ActionBarDrawerToggle;
import android.support.v4.widget.DrawerLayout;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.AdapterView;
import android.widget.Button;
import android.widget.ListView;
public class MainActivity extends Activity{
private DrawerLayout mDrawerLayout;
private ListView mDrawerList;
private ActionBarDrawerToggle mDrawerToggle;
// nav drawer title
private CharSequence mDrawerTitle;
// used to store app title
private CharSequence mTitle;
// slide menu items
private String[] navMenuTitles;
private TypedArray navMenuIcons;
private ArrayList<NavDrawerItem> navDrawerItems;
private NavDrawerListAdapter adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button btnCall = (Button) findViewById(R.id.btnCall);
btnCall.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
Intent intent = new Intent(Intent.ACTION_DIAL);
intent.setData(Uri.parse("tel:1231231234"));
startActivity(intent);
}
});
mTitle = mDrawerTitle = getTitle();
// load slide menu items
navMenuTitles = getResources().getStringArray(R.array.nav_drawer_items);
// nav drawer icons from resources
navMenuIcons = getResources()
.obtainTypedArray(R.array.nav_drawer_icons);
mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
mDrawerList = (ListView) findViewById(R.id.list_slidermenu);
navDrawerItems = new ArrayList<NavDrawerItem>();
// adding nav drawer items to array
// Home
navDrawerItems.add(new NavDrawerItem(navMenuTitles[0], navMenuIcons.getResourceId(0, -1)));
// Find People
navDrawerItems.add(new NavDrawerItem(navMenuTitles[1], navMenuIcons.getResourceId(1, -1)));
// Photos
navDrawerItems.add(new NavDrawerItem(navMenuTitles[2], navMenuIcons.getResourceId(2, -1)));
// Communities, Will add a counter here
navDrawerItems.add(new NavDrawerItem(navMenuTitles[3], navMenuIcons.getResourceId(3, -1)));
// Pages
navDrawerItems.add(new NavDrawerItem(navMenuTitles[4], navMenuIcons.getResourceId(4, -1)));
// What's hot, We will add a counter here
navDrawerItems.add(new NavDrawerItem(navMenuTitles[5], navMenuIcons.getResourceId(5, -1)));
// Recycle the typed array
navMenuIcons.recycle();
mDrawerList.setOnItemClickListener(new SlideMenuClickListener());
// setting the nav drawer list adapter
adapter = new NavDrawerListAdapter(getApplicationContext(),
navDrawerItems);
mDrawerList.setAdapter(adapter);
// enabling action bar app icon and behaving it as toggle button
getActionBar().setDisplayHomeAsUpEnabled(true);
getActionBar().setHomeButtonEnabled(true);
mDrawerToggle = new ActionBarDrawerToggle(this, mDrawerLayout,
R.drawable.ic_drawer, //nav menu toggle icon
R.string.app_name, // nav drawer open - description for accessibility
R.string.app_name // nav drawer close - description for accessibility
) {
public void onDrawerClosed(View view) {
getActionBar().setTitle(mTitle);
// calling onPrepareOptionsMenu() to show action bar icons
invalidateOptionsMenu();
}
public void onDrawerOpened(View drawerView) {
getActionBar().setTitle(mDrawerTitle);
// calling onPrepareOptionsMenu() to hide action bar icons
invalidateOptionsMenu();
}
};
mDrawerLayout.setDrawerListener(mDrawerToggle);
if (savedInstanceState == null) {
// on first time display view for first nav item
displayView(0);
}
}
/**
* Slide menu item click listener
* */
private class SlideMenuClickListener implements
ListView.OnItemClickListener {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position,
long id) {
// display view for selected nav drawer item
displayView(position);
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// toggle nav drawer on selecting action bar app icon/title
if (mDrawerToggle.onOptionsItemSelected(item)) {
return true;
}
// Handle action bar actions click
switch (item.getItemId()) {
case R.id.action_settings:
return true;
default:
return super.onOptionsItemSelected(item);
}
}
/* *
* Called when invalidateOptionsMenu() is triggered
*/
@Override
public boolean onPrepareOptionsMenu(Menu menu) {
// if nav drawer is opened, hide the action items
boolean drawerOpen = mDrawerLayout.isDrawerOpen(mDrawerList);
menu.findItem(R.id.action_settings).setVisible(!drawerOpen);
return super.onPrepareOptionsMenu(menu);
}
/**
* Diplaying fragment view for selected nav drawer list item
* */
private void displayView(int position) {
// update the main content by replacing fragments
Fragment fragment = null;
switch (position) {
case 0:
fragment = new HomeFragment();
break;
case 1:
fragment = new FindPeopleFragment();
break;
case 2:
fragment = new PhotosFragment();
break;
case 3:
fragment = new CommunityFragment();
break;
case 4:
fragment = new PagesFragment();
break;
case 5:
fragment = new WhatsHotFragment();
break;
default:
break;
}
if (fragment != null) {
FragmentManager fragmentManager = getFragmentManager();
fragmentManager.beginTransaction()
.replace(R.id.frame_container, fragment).commit();
// update selected item and title, then close the drawer
mDrawerList.setItemChecked(position, true);
mDrawerList.setSelection(position);
setTitle(navMenuTitles[position]);
mDrawerLayout.closeDrawer(mDrawerList);
} else {
// error in creating fragment
Log.e("MainActivity", "Error in creating fragment");
}
}
@Override
public void setTitle(CharSequence title) {
mTitle = title;
getActionBar().setTitle(mTitle);
}
/**
* When using the ActionBarDrawerToggle, you must call it during
* onPostCreate() and onConfigurationChanged()...
*/
@Override
protected void onPostCreate(Bundle savedInstanceState) {
super.onPostCreate(savedInstanceState);
// Sync the toggle state after onRestoreInstanceState has occurred.
mDrawerToggle.syncState();
}
@Override
public void onConfigurationChanged(Configuration newConfig) {
super.onConfigurationChanged(newConfig);
// Pass any configuration change to the drawer toggls
mDrawerToggle.onConfigurationChanged(newConfig);
}
}
logcat的：
12-27 07:06:03.832: E/AndroidRuntime(6925): at info.androidhive.slidingmenu.MainActivity.onCreate(MainActivity.java:54)
12-27 07:06:03.832: E/AndroidRuntime(6925): at android.app.Activity.performCreate(Activity.java:5231)
12-27 07:06:03.832: E/AndroidRuntime(6925): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
12-27 07:06:03.832: E/AndroidRuntime(6925): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2169)
12-27 07:06:03.832: E/AndroidRuntime(6925): ... 11 more
12-27 07:06:50.167: E/AndroidRuntime(7099): FATAL EXCEPTION: main
12-27 07:06:50.167: E/AndroidRuntime(7099): Process: info.androidhive.slidingmenu, PID: 7099
12-27 07:06:50.167: E/AndroidRuntime(7099): java.lang.RuntimeException: Unable to start activity ComponentInfo{info.androidhive.slidingmenu/info.androidhive.slidingmenu.MainActivity}: java.lang.NullPointerException
12-27 07:06:50.167: E/AndroidRuntime(7099): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2215)
12-27 07:06:50.167: E/AndroidRuntime(7099): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2265)
12-27 07:06:50.167: E/AndroidRuntime(7099): at android.app.ActivityThread.access$800(ActivityThread.java:145)
12-27 07:06:50.167: E/AndroidRuntime(7099): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1206)
12-27 07:06:50.167: E/AndroidRuntime(7099): at android.os.Handler.dispatchMessage(Handler.java:102)
12-27 07:06:50.167: E/AndroidRuntime(7099): at android.os.Looper.loop(Looper.java:136)
12-27 07:06:50.167: E/AndroidRuntime(7099): at android.app.ActivityThread.main(ActivityThread.java:5081)
12-27 07:06:50.167: E/AndroidRuntime(7099): at java.lang.reflect.Method.invokeNative(Native Method)
12-27 07:06:50.167: E/AndroidRuntime(7099): at java.lang.reflect.Method.invoke(Method.java:515)
12-27 07:06:50.167: E/AndroidRuntime(7099): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:781)
12-27 07:06:50.167: E/AndroidRuntime(7099): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
12-27 07:06:50.167: E/AndroidRuntime(7099): at dalvik.system.NativeStart.main(Native Method)
12-27 07:06:50.167: E/AndroidRuntime(7099): Caused by: java.lang.NullPointerException
12-27 07:06:50.167: E/AndroidRuntime(7099): at info.androidhive.slidingmenu.MainActivity.onCreate(MainActivity.java:54)
12-27 07:06:50.167: E/AndroidRuntime(7099): at android.app.Activity.performCreate(Activity.java:5231)
12-27 07:06:50.167: E/AndroidRuntime(7099): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
12-27 07:06:50.167: E/AndroidRuntime(7099): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2169)
12-27 07:06:50.167: E/AndroidRuntime(7099): ... 11 more
答案 0 :(得分：2)
问题不在于setOnClick侦听器本身，而在于findViewById
Button btnCall = (Button) findViewById(R.id.btnCall);
btnCall.setOnClickListener(new View.OnClickListener()
findViewVyId返回null（可能是因为未在布局xml文件中定义btnCall）。 这导致下一行失败并出现NullPointerException。 查看您的activity_main.xml布局文件。你确定你指的是正确的按钮Id并且它是在这个活动中定义的吗？