这是抽屉活动代码 滑动：
public class sliding extends Activity {
// Within which the entire activity is enclosed
private DrawerLayout mDrawerLayout;
// ListView represents Navigation Drawer
private ListView mDrawerList;
// ActionBarDrawerToggle indicates the presence of Navigation Drawer in the
// action bar
private ActionBarDrawerToggle mDrawerToggle;
// Title of the action bar
private String mTitle = "";
@SuppressLint("NewApi")
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.layout_sliding);
}
void Drawer() {
mTitle = "Care&Cure";
getActionBar().setTitle(mTitle);
// Getting reference to the DrawerLayout
mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
mDrawerList = (ListView) findViewById(R.id.drawer_list);
// Getting reference to the ActionBarDrawerToggle
mDrawerToggle = new ActionBarDrawerToggle(this, mDrawerLayout,
R.drawable.ic_drawer, R.string.drawer_open,
R.string.drawer_close) {
/** Called when drawer is closed */
public void onDrawerClosed(View view) {
getActionBar().setTitle(mTitle);
invalidateOptionsMenu();
}
/** Called when a drawer is opened */
public void onDrawerOpened(View drawerView) {
getActionBar().setTitle("Care&Cure");
invalidateOptionsMenu();
}
};
// Setting DrawerToggle on DrawerLayout
mDrawerLayout.setDrawerListener(mDrawerToggle);
// Creating an ArrayAdapter to add items to the listview mDrawerList
ArrayAdapter<String> adapter = new ArrayAdapter<String>(
getBaseContext(), R.layout.drawer_list_item, getResources()
.getStringArray(R.array.menus));
// Setting the adapter on mDrawerList
mDrawerList.setAdapter(adapter);
// Enabling Home button
getActionBar().setHomeButtonEnabled(true);
// Enabling Up navigation
getActionBar().setDisplayHomeAsUpEnabled(true);
// Setting item click listener for the listview mDrawerList
mDrawerList.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
}
});
}
@Override
protected void onPostCreate(Bundle savedInstanceState) {
super.onPostCreate(savedInstanceState);
mDrawerToggle.syncState();
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
if (mDrawerToggle.onOptionsItemSelected(item)) {
return true;
}
return super.onOptionsItemSelected(item);
}
/** Called whenever we call invalidateOptionsMenu() */
@Override
public boolean onPrepareOptionsMenu(Menu menu) {
// If the 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);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
和主要活动 MainActivty：
public class MainActivity extends sliding implements OnClickListener {
ImageButton hosp, doc;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Drawer();
hosp = (ImageButton) findViewById(R.id.btn_hosp);
doc = (ImageButton) findViewById(R.id.btn_doc);
hosp.setOnClickListener(this);
doc.setOnClickListener(this);
}
@Override
public void onClick(View v) {
int id = v.getId();
if (id == R.id.btn_doc) {
Intent dc = new Intent(MainActivity.this, sliding.class);
startActivity(dc);
}
activity_main.xml中
<?xml version="1.0" encoding="utf-8"?>
<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" >
<ScrollView
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="@drawable/bacground" >
<TableLayout
android:id="@+id/tableLayout1"
android:layout_width="fill_parent"
android:layout_height="wrap_content" >
<!-- 2 columns -->
<TableRow
android:id="@+id/tableRow1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="30dp" >
<ImageButton
android:id="@+id/btn_hos"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:background="@drawable/selector"
android:contentDescription="@string/image"
android:src="@drawable/hos" />
<ImageButton
android:id="@+id/btn_doc"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:background="@drawable/selector"
android:contentDescription="@string/image"
android:src="@drawable/doc" />
</TableRow>
<TableRow
android:id="@+id/tableRow2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="30dp" >
<ImageButton
android:id="@+id/btn_lab"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:background="@drawable/selector"
android:contentDescription="@string/image"
android:src="@drawable/lab" />
<ImageButton
android:id="@+id/btn_b"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:background="@drawable/selector"
android:contentDescription="@string/image"
android:src="@drawable/b" />
</TableRow>
</TableLayout>
</ScrollView>
</android.support.v4.widget.DrawerLayout>
logcat的：
08-26 14:25:24.268: W/dalvikvm(17531): threadid=1: thread exiting with uncaught exception (group=0x40aa8228)
08-26 14:25:24.268: E/AndroidRuntime(17531): FATAL EXCEPTION: main
08-26 14:25:24.268: E/AndroidRuntime(17531): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.careandcure/com.example.careandcure.MainActivity}: java.lang.NullPointerException
08-26 14:25:24.268: E/AndroidRuntime(17531): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2205)
08-26 14:25:24.268: E/AndroidRuntime(17531): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2240)
08-26 14:25:24.268: E/AndroidRuntime(17531): at android.app.ActivityThread.access$600(ActivityThread.java:139)
08-26 14:25:24.268: E/AndroidRuntime(17531): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1262)
08-26 14:25:24.268: E/AndroidRuntime(17531): at android.os.Handler.dispatchMessage(Handler.java:99)
08-26 14:25:24.268: E/AndroidRuntime(17531): at android.os.Looper.loop(Looper.java:156)
08-26 14:25:24.268: E/AndroidRuntime(17531): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
08-26 14:25:24.268: E/AndroidRuntime(17531): at dalvik.system.NativeStart.main(Native Method)
08-26 14:25:24.268: E/AndroidRuntime(17531): Caused by: java.lang.NullPointerException
08-26 14:25:24.268: E/AndroidRuntime(17531): at com.example.careandcure.sliding.Drawer(sliding.java:78)
08-26 14:25:24.268: E/AndroidRuntime(17531): at com.example.careandcure.MainActivity.onCreate(MainActivity.java:20)
08-26 14:25:24.268: E/AndroidRuntime(17531): at android.app.Activity.performCreate(Activity.java:4538)
08-26 14:25:24.268: E/AndroidRuntime(17531): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1071)
08-26 14:25:24.268: E/AndroidRuntime(17531): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2161)
我跟随Android Navigation Drawer with multiple activites在多个活动中创建抽屉，它在滑动时工作得很好但在主要活动中没有...给出null pointer exception。如何解决它....提前感谢
答案 0 :(得分：1)
您在覆盖setContentView()的类中调用sliding，在该类中传递要膨胀的新xml文件（R.layout.activity_main）。我的猜测是这个xml文件没有包含sliding Activity所需的布局。
您所关注的示例并不是一个好例子。您正在尝试拥有一个托管NavigationDrawer的Activity，然后扩展该Activity。这个概念很好，但你的执行是错误的。您的滑块类需要能够创建并显示NavigationDrawer并且仍然可以扩展，因此您需要以覆盖标准方法（如onCreate()和调用setContentView()）的方式编写它）不影响滑块类显示NavigationDrawer。
我建议在片段中创建NavigationDrawer，并在滑动onCreate()的{{1}}中对该片段进行充气。这样Activity完全包含在片段中，您不必担心覆盖哪些方法以及使用它们做什么。
答案 1 :(得分：0)
您正在尝试查找ID为btn_hos和btn_hosp的按钮。它给出了一个空指针。
hosp =（ImageButton）findViewById（ R.id.btn_hosp ）;
<ImageButton
android:id="@+id/btn_hos" <----------
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:background="@drawable/selector"
android:contentDescription="@string/image"
android:src="@drawable/hos" />