安卓系统中的setVisibility(View.INVISIBLE)无法工作

Question

两天来，我一直在尝试让setVisibility(View.INVISIBLE)函数正常工作。但是如果我在模拟器中测试我的应用程序，它总是崩溃。怎么了？(还有：onClickListener中的视图arg0和v有什么区别？)

public class SpielActivity extends Activity {


@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_spiel);

    final Button startbutton = (Button)findViewById(R.id.anfangsbutton);
    final TextView initCountdown = (TextView)findViewById(R.id.initcountdown);

    startbutton.setVisibility(View.VISIBLE);

   startbutton.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View arg0) { 
            startbutton.setVisibility(View.INVISIBLE);
             new CountDownTimer(3500, 1000) {

                 public void onTick(long millisUntilFinished) {
                     initCountdown.setText("" + millisUntilFinished / 1000);
                 }

                 public void onFinish() {
                     initCountdown.setText("");
                 }
              }.start();



        }
    });
    }

}

下面是LogCat数据：

02-12 14:18:30.147: W/dalvikvm(332): threadid=1: thread exiting with uncaught exception (group=0x40015560)
02-12 14:18:30.147: E/AndroidRuntime(332): FATAL EXCEPTION: main
02-12 14:18:30.147: E/AndroidRuntime(332): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.JodomStudios.cloudgame/com.JodomStudios.cloudgame.SpielActivity}: java.lang.ClassCastException: android.widget.ImageButton
02-12 14:18:30.147: E/AndroidRuntime(332):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
02-12 14:18:30.147: E/AndroidRuntime(332):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
02-12 14:18:30.147: E/AndroidRuntime(332):  at android.app.ActivityThread.access(ActivityThread.java:117)
02-12 14:18:30.147: E/AndroidRuntime(332):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
02-12 14:18:30.147: E/AndroidRuntime(332):  at android.os.Handler.dispatchMessage(Handler.java:99)
02-12 14:18:30.147: E/AndroidRuntime(332):  at android.os.Looper.loop(Looper.java:123)
02-12 14:18:30.147: E/AndroidRuntime(332):  at android.app.ActivityThread.main(ActivityThread.java:3683)
02-12 14:18:30.147: E/AndroidRuntime(332):  at java.lang.reflect.Method.invokeNative(Native Method)
02-12 14:18:30.147: E/AndroidRuntime(332):  at java.lang.reflect.Method.invoke(Method.java:507)
02-12 14:18:30.147: E/AndroidRuntime(332):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
02-12 14:18:30.147: E/AndroidRuntime(332):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
02-12 14:18:30.147: E/AndroidRuntime(332):  at dalvik.system.NativeStart.main(Native Method)
02-12 14:18:30.147: E/AndroidRuntime(332): Caused by: java.lang.ClassCastException: android.widget.ImageButton
02-12 14:18:30.147: E/AndroidRuntime(332):  at com.JodomStudios.cloudgame.SpielActivity.onCreate(SpielActivity.java:19)
02-12 14:18:30.147: E/AndroidRuntime(332):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
02-12 14:18:30.147: E/AndroidRuntime(332):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
02-12 14:18:30.147: E/AndroidRuntime(332):  ... 11 more

下面是xml布局

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/linearlayoutspiel"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@drawable/backgroundleiter"
    android:orientation="vertical" >

    <TextView
        android:id="@+id/zeitzaehler"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:text="@string/countdown"
        android:textAppearance="?android:attr/textAppearanceMedium" />

    <Button
        android:id="@+id/menubutton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_alignParentRight="true"
        android:text="@string/menu" />

    <Button
        android:id="@+id/contbutton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_alignParentLeft="true"
        android:text="@string/cont" />

    <ImageButton
        android:id="@+id/pausebutton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentRight="true"
        android:layout_alignParentTop="true"
        android:background="#00000000"
        android:src="@drawable/closebutton" />

    <TextView
        android:id="@+id/initcountdown"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:text="@string/initcountdown"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:textSize="40sp" />

    <ImageButton
        android:id="@+id/retrybutton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_toLeftOf="@+id/pausebutton"
        android:background="#00000000"
        android:src="@drawable/zeichnung" />

    <Button
        android:id="@+id/anfangsbutton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_above="@+id/menubutton"
        android:layout_centerHorizontal="true"
        android:layout_marginBottom="18dp"
        android:text="@string/startgame" />

</RelativeLayout>

Answer 1

我认为你的应用程序也可能会崩溃，因为你更新UI而不是从UI线程。你使用计时器，它在单独的线程中运行。尝试将initCountdown.setText封装到post中：

initCountdown.post(new Runnable() {
public void run() {
initCountdown.setText("" + millisUntilFinished / 1000);
}
});

Answer 2

您正在使用start按钮作为按钮，并在XML.Please中定义了一个ImageButton，使它们相同。

Answer 3

从日志中：

02-12 14:18:30.147: E/AndroidRuntime(332): Caused by: java.lang.ClassCastException: android.widget.ImageButton

似乎您正在使用的检索按钮

final Button startbutton = (Button)findViewById(R.id.anfangsbutton);

不是Button，因此也不是ClassCastException。请验证您的布局xml并使用正确的强制转换。

希望这能有所帮助。