我一直在按照教程来获取每个活动的导航抽屉：
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);
// set a custom shadow that overlays the main content when the drawer opens
//mDrawerLayout.setDrawerShadow(R.drawable.drawer_shadow, GravityCompat.START);
// set up the drawer's list view with items and click listener
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.string.drawer_open, /* "open drawer" description for accessibility */
R.string.drawer_close) /* "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; //Setting currently selected position in this field so that it will be available in our child activities.
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.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);
}
}
}
我得到一个空指针异常：
java.lang.NullPointerException
at net.udazz.udazz.BaseActivity.onCreate(BaseActivity.java:91)
at net.udazz.udazz.MainActivity.onCreate(MainActivity.java:36)
我尝试用onCreate替换onCreateDrawer，但它没有帮助
这是自定义主题的代码：
<?xml version="1.0" encoding="utf-8"?>
<resources>
<!-- the theme applied to the application or activity -->
<style name="CustomActionBarTheme"
parent="@style/Theme.AppCompat.Light.DarkActionBar">
<item name="android:actionBarStyle">@style/MyActionBar</item>
<!-- colorPrimary is used for the default action bar background -->
<item name="colorPrimary">@color/color_primary</item>
<!-- colorPrimaryDark is used for the status bar -->
<item name="colorPrimaryDark">@color/status_bar_color</item>
<!-- colorAccent is used as the default value for colorControlActivated
which is used to tint widgets -->
<item name="colorAccent">@color/accent</item>
<!-- Support library compatibility -->
<item name="actionBarStyle">@style/MyActionBar</item>
</style>
<!-- ActionBar styles -->
<style name="MyActionBar"
parent="@style/Widget.AppCompat.Light.ActionBar.Solid.Inverse">
<item name="android:background">@drawable/actionbar_background</item>
<!-- Support library compatibility -->
<item name="background">@drawable/actionbar_background</item>
</style>
</resources>
MainActivity：我认为问题出在setContentView中。我在这个Activity中需要WebView。这是代码：
public class MainActivity extends AppCompatActivity {
private WebView mWebView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mWebView = (WebView) findViewById(R.id.activity_main_webview);
// Enable Javascript
WebSettings webSettings = mWebView.getSettings();
webSettings.setJavaScriptEnabled(true);
//Hide the semy cirle at th bottom of the action bar when the user slides to the top
mWebView.setOverScrollMode(WebView.OVER_SCROLL_NEVER);
mWebView.getSettings().setLoadWithOverviewMode(true);
mWebView.getSettings().setUseWideViewPort(true);
//mainWebView.setWebViewClient(new WebViewClient());
mWebView.setWebViewClient(new WebViewClient() {
@Override
public void onReceivedError(WebView view, int errorCode, String description, String failingUrl) {
view.stopLoading(); // may not be needed
view.loadUrl("file:///android_asset/errorPage.HTML");
}
@Override
public void onPageFinished(WebView view, String url) {
//sendRegistrationIdToBackend();
//getCookies();
}
@Override
public boolean shouldOverrideUrlLoading(WebView view, String url) {
if (url.contains("pics")) {
Intent a = new Intent(MainActivity.this, MyPostsActivity.class);
startActivity(a);
} else if (Uri.parse(url).getHost().length() == 0) {
return false;
} else { // Otherwise, give the default behavior (open in browser)
mWebView.loadUrl(url);
}
return true;
}
});
mWebView.loadUrl("http://url/");
// Stop local links and redirects from opening in browser instead of WebView
// mWebView.setWebViewClient(new MyAppWebViewClient());
}
@Override
public void onBackPressed(){
super.onBackPressed();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}