我想在平板电脑中保持导航抽屉打开。要做到这一点，我使用以下代码，但当我触摸内容框架时，我得到空指针异常。
我的XML文件：
<FrameLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.v4.widget.DrawerLayout
android:id="@+id/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent">
<!-- The navigation drawer -->
<ListView
android:id="@+id/left_drawer"
android:layout_width="@dimen/drawer_size"
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>
<FrameLayout
android:id="@+id/content_frame"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginLeft="@dimen/drawer_content_padding"/>
</FrameLayout>
Mainactivity：
public class MainActivity extends FragmentActivity {
private boolean isDrawerLocked = false;
private ListView drawerList;
private DrawerLayout drawerLayout;
private String[] drawerItems;
private ActionBarDrawerToggle drawerToggle;
@Override
protected void onCreate(Bundle bundle) {
super.onCreate(bundle);
setContentView(R.layout.activity_main);
drawerList = (ListView) findViewById(R.id.left_drawer);
drawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
FrameLayout frameLayout = (FrameLayout)findViewById(R.id.content_frame);
if(((ViewGroup.MarginLayoutParams)frameLayout.getLayoutParams()).leftMargin == (int)getResources().getDimension(R.dimen.drawer_size)) {
drawerLayout.setDrawerLockMode(DrawerLayout.LOCK_MODE_LOCKED_OPEN, drawerList);
drawerLayout.setScrimColor(Color.TRANSPARENT);
isDrawerLocked = true;
}
// Set the adapter for the list view
drawerItems = getResources().getStringArray(R.array.Guide_elements);
drawerToggle = new ActionBarDrawerToggle(
this,
drawerLayout,
R.drawable.ic_drawer,
R.string.app_name,
R.string.app_name
) {
/** Called when a drawer has settled in a completely closed state. */
public void onDrawerClosed(View view) {
getActionBar().setTitle(getTitle());
invalidateOptionsMenu();
}
/** Called when a drawer has settled in a completely open state. */
public void onDrawerOpened(View drawerView) {
getActionBar().setTitle("Select Option");
invalidateOptionsMenu();
}
};
if(!isDrawerLocked) {
drawerLayout.setDrawerListener(drawerToggle);
}
// Set the drawer toggle as the DrawerListener
DrawerItemClickListener drawerItemClickListener = new DrawerItemClickListener();
drawerList.setOnItemClickListener(drawerItemClickListener);
if(!isDrawerLocked) {
getActionBar().setDisplayHomeAsUpEnabled(true);
}
}
@Override
protected void onPostCreate(Bundle savedInstanceState) {
super.onPostCreate(savedInstanceState);
drawerToggle.syncState();
}
@Override
public void onConfigurationChanged(Configuration newConfig) {
super.onConfigurationChanged(newConfig);
drawerToggle.onConfigurationChanged(newConfig);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Pass the event to ActionBarDrawerToggle, if it returns
// true, then it has handled the app icon touch event
if (drawerToggle.onOptionsItemSelected(item)) {
return true;
}
return super.onOptionsItemSelected(item);
}
@Override
public boolean onPrepareOptionsMenu(Menu menu) {
// If the nav drawer is open, hide action items related to the content view
boolean drawerOpen = drawerLayout.isDrawerOpen(drawerList);
MenuItem item = menu.findItem(R.id.action_settings);
if(item != null) {
item.setVisible(!drawerOpen);
}
item = menu.findItem(R.id.action_settings);
if(item != null) {
item.setVisible(!drawerOpen);
}
return super.onPrepareOptionsMenu(menu);
}
/**
* The drawer item click listener
*/
private class DrawerItemClickListener implements ListView.OnItemClickListener {
@Override
public void onItemClick(AdapterView parent, View view, int position, long id) {
selectItem(position);
}
/** Swaps fragments in the main content view */
private void selectItem(int position) {
Bundle bundle;
switch(position) {
}
FragmentManager fragmentManager = getFragmentManager();
fragmentManager.beginTransaction()
.replace(R.id.content_frame, null)
.commit();
// Highlight the selected item, update the title, and close the drawer
drawerList.setItemChecked(position, true);
setTitle(MainActivity.this.drawerItems[position]);
if(!isDrawerLocked) {
drawerLayout.closeDrawer(drawerList);
}
}
}
}
但是当我触及content_frame时，我得到空指针异常。如何解决问题以避免空指针异常。
例外详情：
10-30 12:53:42.374: E/InputEventReceiver(3157): Exception dispatching input event.
10-30 12:53:42.374: E/MessageQueue-JNI(3157): Exception in MessageQueue callback: handleReceiveCallback
10-30 12:53:42.414: E/MessageQueue-JNI(3157): java.lang.NullPointerException
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at android.support.v4.widget.DrawerLayout.isContentView(DrawerLayout.java:853)
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at android.support.v4.widget.DrawerLayout.onInterceptTouchEvent(DrawerLayout.java:879)
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1854)
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2211)
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1912)
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2211)
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1912)
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2211)
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1912)
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2211)
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1912)
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:1966)
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1418)
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at android.app.Activity.dispatchTouchEvent(Activity.java:2424)
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1914)
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at android.view.View.dispatchPointerEvent(View.java:7564)
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at android.view.ViewRootImpl$ViewPostImeInputStage.processPointerEvent(ViewRootImpl.java:3883)
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:3778)
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3379)
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3429)
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3398)
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:3483)
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3406)
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:3540)
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3379)
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3429)
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3398)
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3406)
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3379)
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:5419)
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:5399)
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:5370)
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at android.view.ViewRootImpl$WindowInputEventReceiver.onInputEvent(ViewRootImpl.java:5493)
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at android.view.InputEventReceiver.dispatchInputEvent(InputEventReceiver.java:182)
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at android.os.MessageQueue.nativePollOnce(Native Method)
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at android.os.MessageQueue.next(MessageQueue.java:132)
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at android.os.Looper.loop(Looper.java:124)
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at android.app.ActivityThread.main(ActivityThread.java:5103)
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at java.lang.reflect.Method.invokeNative(Native Method)
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at java.lang.reflect.Method.invoke(Method.java:525)
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
10-30 12:53:42.414: E/MessageQueue-JNI(3157): at dalvik.system.NativeStart.main(Native Method)
10-30 12:53:42.434: W/dalvikvm(3157): threadid=1: thread exiting with uncaught exception (group=0x41465700)
10-30 12:53:42.484: E/AndroidRuntime(3157): FATAL EXCEPTION: main
10-30 12:53:42.484: E/AndroidRuntime(3157): java.lang.NullPointerException
10-30 12:53:42.484: E/AndroidRuntime(3157): at android.support.v4.widget.DrawerLayout.isContentView(DrawerLayout.java:853)
10-30 12:53:42.484: E/AndroidRuntime(3157): at android.support.v4.widget.DrawerLayout.onInterceptTouchEvent(DrawerLayout.java:879)
10-30 12:53:42.484: E/AndroidRuntime(3157): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1854)
10-30 12:53:42.484: E/AndroidRuntime(3157): at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2211)
10-30 12:53:42.484: E/AndroidRuntime(3157): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1912)
10-30 12:53:42.484: E/AndroidRuntime(3157): at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2211)
10-30 12:53:42.484: E/AndroidRuntime(3157): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1912)
10-30 12:53:42.484: E/AndroidRuntime(3157): at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2211)
10-30 12:53:42.484: E/AndroidRuntime(3157): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1912)
10-30 12:53:42.484: E/AndroidRuntime(3157): at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2211)
10-30 12:53:42.484: E/AndroidRuntime(3157): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1912)
10-30 12:53:42.484: E/AndroidRuntime(3157): at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:1966)
10-30 12:53:42.484: E/AndroidRuntime(3157): at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1418)
10-30 12:53:42.484: E/AndroidRuntime(3157): at android.app.Activity.dispatchTouchEvent(Activity.java:2424)
10-30 12:53:42.484: E/AndroidRuntime(3157): at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1914)
10-30 12:53:42.484: E/AndroidRuntime(3157): at android.view.View.dispatchPointerEvent(View.java:7564)
10-30 12:53:42.484: E/AndroidRuntime(3157): at android.view.ViewRootImpl$ViewPostImeInputStage.processPointerEvent(ViewRootImpl.java:3883)
10-30 12:53:42.484: E/AndroidRuntime(3157): at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:3778)
10-30 12:53:42.484: E/AndroidRuntime(3157): at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3379)
10-30 12:53:42.484: E/AndroidRuntime(3157): at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3429)
10-30 12:53:42.484: E/AndroidRuntime(3157): at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3398)
10-30 12:53:42.484: E/AndroidRuntime(3157): at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:3483)
10-30 12:53:42.484: E/AndroidRuntime(3157): at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3406)
10-30 12:53:42.484: E/AndroidRuntime(3157): at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:3540)
10-30 12:53:42.484: E/AndroidRuntime(3157): at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3379)
10-30 12:53:42.484: E/AndroidRuntime(3157): at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3429)
10-30 12:53:42.484: E/AndroidRuntime(3157): at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3398)
10-30 12:53:42.484: E/AndroidRuntime(3157): at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3406)
10-30 12:53:42.484: E/AndroidRuntime(3157): at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3379)
10-30 12:53:42.484: E/AndroidRuntime(3157): at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:5419)
10-30 12:53:42.484: E/AndroidRuntime(3157): at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:5399)
10-30 12:53:42.484: E/AndroidRuntime(3157): at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:5370)
10-30 12:53:42.484: E/AndroidRuntime(3157): at android.view.ViewRootImpl$WindowInputEventReceiver.onInputEvent(ViewRootImpl.java:5493)
10-30 12:53:42.484: E/AndroidRuntime(3157): at android.view.InputEventReceiver.dispatchInputEvent(InputEventReceiver.java:182)
10-30 12:53:42.484: E/AndroidRuntime(3157): at android.os.MessageQueue.nativePollOnce(Native Method)
10-30 12:53:42.484: E/AndroidRuntime(3157): at android.os.MessageQueue.next(MessageQueue.java:132)
10-30 12:53:42.484: E/AndroidRuntime(3157): at android.os.Looper.loop(Looper.java:124)
10-30 12:53:42.484: E/AndroidRuntime(3157): at android.app.ActivityThread.main(ActivityThread.java:5103)
10-30 12:53:42.484: E/AndroidRuntime(3157): at java.lang.reflect.Method.invokeNative(Native Method)
10-30 12:53:42.484: E/AndroidRuntime(3157): at java.lang.reflect.Method.invoke(Method.java:525)
10-30 12:53:42.484: E/AndroidRuntime(3157): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
10-30 12:53:42.484: E/AndroidRuntime(3157): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
10-30 12:53:42.484: E/AndroidRuntime(3157): at dalvik.system.NativeStart.main(Native Method)
答案 0 :(得分：0)
如何解决问题以避免空指针异常
我认为你的Naivagtion抽屉里有bcoz。
必须有两个布局。
当抽屉打开视图时，第一个布局将位于后端 从后面出现
第二个布局用于前视图，即未打开抽屉时。
所以，
尝试在ListView下面的Drawer Layout中添加第二个布局。
例如
<android.support.v4.widget.DrawerLayout
android:id="@+id/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent">
<!-- The navigation drawer -->
<ListView
android:id="@+id/left_drawer"
android:layout_width="@dimen/drawer_size"
android:layout_height="match_parent"
android:layout_gravity="start"
android:choiceMode="singleChoice"
android:divider="@android:color/transparent"
android:dividerHeight="0dp"
android:background="#111"/>
<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="welcome"
android:textAppearance="?android:attr/textAppearanceLarge"
android:textColor="#090" />
</android.support.v4.widget.DrawerLayout>
答案 1 :(得分：0)
您需要为ListView drawerItems的字符串数组drawerList创建一个适配器。
答案 2 :(得分：0)
您也可以将抽屉始终打开...只需将其内容放在主布局中，然后移除DrawerLayout。您可以通过providing平板电脑的不同布局资源轻松实现此目的，其中您的抽屉内容直接放置在根布局中。