我正在使用导航抽屉制作一个Android应用程序。我还想在用户第一次打开应用程序时显示透明的指令屏幕。为此,我在我的xml文件中有一个相对的布局,以及一个抽屉的listView。
XML文件:
<android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/drawerLayout"
android:layout_width="match_parent"
android:layout_height="match_parent">
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.twistedlines.overbudget.MainActivity"
tools:ignore="MergeRootFrame" >
<!-- transparent overlay -->
<RelativeLayout
android:id="@+id/top_transparent"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#77CCCCCC" >
<ImageView
android:id="@+id/transparent_img"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:contentDescription="@string/contdesc"
android:scaleType="fitXY"
android:src="@drawable/instructions" />
</RelativeLayout>
</FrameLayout>
<ListView android:id="@+id/drawerList"
android:layout_height="match_parent"
android:layout_width="240dp"
android:layout_gravity="start"
android:divider="#c7c7c7"
android:dividerHeight="3dp"
android:background="#bdbdbd"></ListView>
</android.support.v4.widget.DrawerLayout>
但是,我在这行中的java文件中得到了classCastException:
drawerList = (ListView) findViewById(R.id.drawerList);
logcat的:
11-11 00:10:53.417:E / test(8163):例外11-11 00:10:53.437: E / AndroidRuntime(8163):致命例外:主11-11 00:10:53.437: E / AndroidRuntime(8163):java.lang.RuntimeException:无法启动 活动 ComponentInfo {com.twistedlines.overbudget / com.twistedlines.overbudget.MainActivity}: java.lang.ClassCastException:android.widget.RelativeLayout不能 强制转换为android.widget.ListView 11-11 00:10:53.437: E / AndroidRuntime(8163):at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2062) 11-11 00:10:53.437:E / AndroidRuntime(8163):at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2087) 11-11 00:10:53.437:E / AndroidRuntime(8163):at android.app.ActivityThread.access $ 600(ActivityThread.java:133)11-11 00:10:53.437:E / AndroidRuntime(8163):at android.app.ActivityThread $ H.handleMessage(ActivityThread.java:1198) 11-11 00:10:53.437:E / AndroidRuntime(8163):at android.os.Handler.dispatchMessage(Handler.java:99)11-11 00:10:53.437:E / AndroidRuntime(8163):at android.os.Looper.loop(Looper.java:137)11-11 00:10:53.437: E / AndroidRuntime(8163):at android.app.ActivityThread.main(ActivityThread.java:4792)11-11 00:10:53.437:E / AndroidRuntime(8163):at java.lang.reflect.Method.invokeNative(Native Method)11-11 00:10:53.437:E / AndroidRuntime(8163):at java.lang.reflect.Method.invoke(Method.java:511)11-11 00:10:53.437: E / AndroidRuntime(8163):at com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run(ZygoteInit.java:808) 11-11 00:10:53.437:E / AndroidRuntime(8163):at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:575)11-11 00:10:53.437:E / AndroidRuntime(8163):at dalvik.system.NativeStart.main(Native Method)11-11 00:10:53.437: E / AndroidRuntime(8163):引起:java.lang.ClassCastException: android.widget.RelativeLayout无法强制转换为 android.widget.ListView 11-11 00:10:53.437:E / AndroidRuntime(8163): 在 com.twistedlines.overbudget.MainActivity.onCreate(MainActivity.java:118) 11-11 00:10:53.437:E / AndroidRuntime(8163):at android.app.Activity.performCreate(Activity.java:5008)11-11 00:10:53.437:E / AndroidRuntime(8163):at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079) 11-11 00:10:53.437:E / AndroidRuntime(8163):at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2026)
它说RelativeLayout不能投射到ListView。但在我的XML中,drawerList是ListView,而不是RelativeLayout。有什么问题?
我的drawerList变量是一个ListView对象。这是宣言:
DrawerLayout drawerLayout;
ListView drawerList;
ActionBarDrawerToggle abdToggle;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
topLevelLayout = findViewById(R.id.top_transparent);
if (isFirstTime()) {
topLevelLayout.setVisibility(View.INVISIBLE);
}
drawerLayout = (DrawerLayout)findViewById(R.id.drawerLayout);
drawerList = (ListView) findViewById(R.id.drawerList); //exception line
adaptr=new mAdapter(this);
drawerList.setAdapter(adaptr);
drawerList.setOnItemClickListener(new itemListener());
drawerLayout.setDrawerShadow(R.drawable.drawer_shadow,
GravityCompat.START);
getSupportActionBar().setTitle("Overview");
//rest of the code
答案 0 :(得分:0)
你的代码对我来说似乎没问题。试着再次清理并重建它。
清洁。 转到项目 - &gt;清洁。选择您的项目,然后单击确定。
要重新重建它,只需运行您的代码。