我正在尝试创建导航抽屉活动，因此我可以通过按照此问题中给出的答案Link来扩展该活动并在所有活动中使用菜单，但我的测试应用程序一直在崩溃，这是我的代码：
BaseActivity.java
public class BaseActivity extends Activity {
public DrawerLayout drawerLayout;
public ListView drawerList;
public String[] layers;
private ActionBarDrawerToggle drawerToggle;
protected void onCreate(Bundle savedInstanceState) {
// R.id.drawer_layout should be in every activity with exactly the same
// id.
drawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
drawerToggle = new ActionBarDrawerToggle((Activity) this, drawerLayout,
R.drawable.ic_drawer, 0, 0) {
public void onDrawerClosed(View view) {
getActionBar().setTitle(R.string.hello_world);
}
public void onDrawerOpened(View drawerView) {
getActionBar().setTitle(R.string.hello_world);
}
};
drawerLayout.setDrawerListener(drawerToggle);
getActionBar().setDisplayHomeAsUpEnabled(true);
getActionBar().setHomeButtonEnabled(true);
layers = getResources().getStringArray(R.array.planets_array);
drawerList = (ListView) findViewById(R.id.left_drawer);
drawerList.setAdapter(new ArrayAdapter<String>(this,
R.layout.drawer_list_item, android.R.id.text1, layers));
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
if (drawerToggle.onOptionsItemSelected(item)) {
return true;
}
return super.onOptionsItemSelected(item);
}
@Override
protected void onPostCreate(Bundle savedInstanceState) {
super.onPostCreate(savedInstanceState);
drawerToggle.syncState();
}
@Override
public void onConfigurationChanged(Configuration newConfig) {
super.onConfigurationChanged(newConfig);
drawerToggle.onConfigurationChanged(newConfig);
}
}
MainActivity.java
public class MainActivity extends BaseActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_profile);
}
}
activity_profile.xml
<RelativeLayout 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"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".ProfileActivity" >
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/hello_world" />
</RelativeLayout>
logcat的
03-03 01:22:18.031: D/AndroidRuntime(27902): Shutting down VM
03-03 01:22:18.031: W/dalvikvm(27902): threadid=1: thread exiting with uncaught exception (group=0x2b542210)
03-03 01:22:18.041: E/AndroidRuntime(27902): FATAL EXCEPTION: main
03-03 01:22:18.041: E/AndroidRuntime(27902): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.slider/com.example.slider.MainActivity}: java.lang.NullPointerException
03-03 01:22:18.041: E/AndroidRuntime(27902): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1967)
03-03 01:22:18.041: E/AndroidRuntime(27902): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1992)
03-03 01:22:18.041: E/AndroidRuntime(27902): at android.app.ActivityThread.access$600(ActivityThread.java:127)
03-03 01:22:18.041: E/AndroidRuntime(27902): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1158)
03-03 01:22:18.041: E/AndroidRuntime(27902): at android.os.Handler.dispatchMessage(Handler.java:99)
03-03 01:22:18.041: E/AndroidRuntime(27902): at android.os.Looper.loop(Looper.java:137)
03-03 01:22:18.041: E/AndroidRuntime(27902): at android.app.ActivityThread.main(ActivityThread.java:4441)
03-03 01:22:18.041: E/AndroidRuntime(27902): at java.lang.reflect.Method.invokeNative(Native Method)
03-03 01:22:18.041: E/AndroidRuntime(27902): at java.lang.reflect.Method.invoke(Method.java:511)
03-03 01:22:18.041: E/AndroidRuntime(27902): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
03-03 01:22:18.041: E/AndroidRuntime(27902): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
03-03 01:22:18.041: E/AndroidRuntime(27902): at dalvik.system.NativeStart.main(Native Method)
03-03 01:22:18.041: E/AndroidRuntime(27902): Caused by: java.lang.NullPointerException
03-03 01:22:18.041: E/AndroidRuntime(27902): at com.example.slider.BaseActivity.onCreate(BaseActivity.java:35)
03-03 01:22:18.041: E/AndroidRuntime(27902): at com.example.slider.MainActivity.onCreate(MainActivity.java:12)
03-03 01:22:18.041: E/AndroidRuntime(27902): at android.app.Activity.performCreate(Activity.java:4465)
03-03 01:22:18.041: E/AndroidRuntime(27902): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
03-03 01:22:18.041: E/AndroidRuntime(27902): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1931)
03-03 01:22:18.041: E/AndroidRuntime(27902): ... 11 more
答案 0 :(得分：5)
问题似乎是基类不知道布局。不知道如何或为什么它为其他人工作而不必做这样的事情..但我是Android新手。
我得到了同样的错误，并通过onCreate将我的布局传递给基地来解决。
所以在基础中，我将onCreate修改为：
protected void onCreate(Bundle savedInstanceState, int resLayoutID)
{
super.onCreate(savedInstanceState);
setContentView(resLayoutID);
然后，从我的新活动开始，我有了这个：
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState, R.layout.my_activity);
我的基础中的代码现在可以使用而不是保持为null：
drawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
drawerList = (ListView) findViewById(R.id.left_drawer);
答案 1 :(得分：5)
在主活动中，你必须在setContentView（）之后调用super.onCreate（savedInstanceState）
答案 2 :(得分：3)
在父 classBaseActivity ：
上声明protected abstract int getLayoutId();
onCreate（）我添加了一行
setContentView(getLayoutId());
现在在您的子类 MainActivity 上实现它，例如：
protected int getLayoutId() {
return R.layout.activity_profile;
}
如果您知道更好的解决方案，请告诉我。
答案 3 :(得分：2)
根据oli的建议，您需要在主要活动中调用 setContentView（R.layout.activity_view） 。
一旦主要活动中的内容视图设置为，就必须调用BaseActivity的onCreate，如下所示：
public class BaseActivity extends Activity {
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// REST Navigation drawer initialization
}
}
public class MainActivity extends BaseActivity {
protected void onCreate(Bundle savedInstanceState) {
setContentView(R.layout.activity_view);
super.onCreate(savedInstanceState);
// REST APPLICATION CODE
}
}
答案 4 :(得分：1)
您的xml文件看起来应该是这样的，取自Android网站：http://developer.android.com/training/implementing-navigation/nav-drawer.html
<android.support.v4.widget.DrawerLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent">
<!-- The main content view -->
<FrameLayout
android:id="@+id/content_frame"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<!-- Add content here -->
</FrameLayout>
<!-- The navigation drawer -->
<ListView android:id="@+id/left_drawer"
android:layout_width="240dp"
android:layout_height="match_parent"
android:layout_gravity="start"
android:choiceMode="singleChoice"
android:divider="@android:color/transparent"
android:dividerHeight="0dp"
android:background="#111"/>
</android.support.v4.widget.DrawerLayout>
答案 5 :(得分：1)
在您 MainActivity 中，只需将<{1}}置于
之前<?php
session_start();
$echoString = "";
foreach($_SESSION as $key => $sessionArr){
if($key == "nama"){
$echoString .= "name : ";
}
else if($key == "nilai"){
$echoString .= "score : ";
}
else{
$echoString .= $key." : ";
}
foreach($sessionArr as $value)
{
$echoString .= $value." ";
}
}
echo $echoString;
?>
如下所示：
setContentView(R.layout.activity_main)