我是Android和Android的新手现在我在我的应用程序中遇到了奇怪的问题。它在控制台中没有给我任何错误。我只是想测试Android的不同通知选项，因此这里是我编写的代码：
class Home extends Activity {
Button notification;
Button progress;
private int ID=1;
ProgressDialog pd;
ProgressTask pt = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_home);
notification=(Button)this.findViewById(R.id.start_notification);
notification.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
StartNotification();
}});
Button background = (Button)this.findViewById(R.id.change_background);
background.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
showDialog(0);
}});
progress.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
showDialog(1);
}});
}
@Override
protected Dialog onCreateDialog(int id)
{
final CharSequence[] items = {"Black","Red", "Green", "Blue", "Gray"};
final String[] color = {"#202020","#D11919", "#339966", "#006699", "#818181"};
switch(id) {
case 0:
return new AlertDialog.Builder(this)
.setTitle("Set Background Color")
.setSingleChoiceItems(items, -1, new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int item) {
View mainLayout = findViewById(R.id.activity_home);
View root = mainLayout.getRootView();
new Color();
root.setBackgroundColor(Color.parseColor(color[item]));
dismissDialog(0);
}
}).create();
case 1:
pd = new ProgressDialog(Home.this);
pd.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
pd.setMessage("Downloading...");
return pd;
}
return null;
}
@Override
protected void onPrepareDialog(int id, Dialog dialog) {
switch(id) {
case 1:
pd.setProgress(0);
pt = new ProgressTask(handler);
pt.start();
}
}
final Handler handler = new Handler() {
public void handleMessage(Message msg) {
int count = msg.arg1;
pd.setProgress(count);
if (count >= 100){
dismissDialog(1);
pt.setStatus(false);
}
}
};
private class ProgressTask extends Thread {
Handler myHandler;
int count = 0;
boolean status = true;
ProgressTask(Handler _handler) {
myHandler = _handler;
}
public void run() {
while (status) {
try {
Thread.sleep(100);
} catch (InterruptedException e) {
e.printStackTrace();
}
Message msg = myHandler.obtainMessage();
msg.arg1 = count;
myHandler.sendMessage(msg);
count++;
}
}
public void setStatus(boolean m){
status = m;
}
}
private void StartNotification()
{
Intent intent= new Intent(Home.this, NotificationView.class);
intent.putExtra("ID", ID);
PendingIntent pendingIntent=PendingIntent.getActivity(Home.this, 0, intent, 0);
NotificationManager nm=(NotificationManager) getSystemService(NOTIFICATION_SERVICE);
Notification notif = new Notification(
R.drawable.ball,"Reminder: Game starts in 15 minutes",
System.currentTimeMillis());
CharSequence from = "Sports Center";
CharSequence message = "Game: L.A Lakers vs Miami Heat";
notif.setLatestEventInfo(this, from, message, pendingIntent);
notif.vibrate = new long[] { 100, 250, 100, 500};
nm.notify(ID, notif);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.activity_home, menu);
return true;
}
}
这是我的日志：
04-21 16:55:03.829: I/dalvikvm(907): threadid=3: reacting to signal 3
04-21 16:55:03.966: I/dalvikvm(907): Wrote stack traces to '/data/anr/traces.txt'
04-21 16:55:04.265: I/dalvikvm(907): threadid=3: reacting to signal 3
04-21 16:55:04.545: D/dalvikvm(907): newInstance failed: Lcom/example/statusbar/Home; not accessible to Landroid/app/Instrumentation;
04-21 16:55:04.545: I/dalvikvm(907): Wrote stack traces to '/data/anr/traces.txt'
04-21 16:55:04.555: D/AndroidRuntime(907): Shutting down VM
04-21 16:55:04.555: W/dalvikvm(907): threadid=1: thread exiting with uncaught exception (group=0x409c01f8)
04-21 16:55:04.595: E/AndroidRuntime(907): FATAL EXCEPTION: main
04-21 16:55:04.595: E/AndroidRuntime(907): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.statusbar/com.example.statusbar.Home}: java.lang.IllegalAccessException: access to class not allowed
04-21 16:55:04.595: E/AndroidRuntime(907): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1880)
04-21 16:55:04.595: E/AndroidRuntime(907): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
04-21 16:55:04.595: E/AndroidRuntime(907): at android.app.ActivityThread.access$600(ActivityThread.java:123)
04-21 16:55:04.595: E/AndroidRuntime(907): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
04-21 16:55:04.595: E/AndroidRuntime(907): at android.os.Handler.dispatchMessage(Handler.java:99)
04-21 16:55:04.595: E/AndroidRuntime(907): at android.os.Looper.loop(Looper.java:137)
04-21 16:55:04.595: E/AndroidRuntime(907): at android.app.ActivityThread.main(ActivityThread.java:4424)
04-21 16:55:04.595: E/AndroidRuntime(907): at java.lang.reflect.Method.invokeNative(Native Method)
04-21 16:55:04.595: E/AndroidRuntime(907): at java.lang.reflect.Method.invoke(Method.java:511)
04-21 16:55:04.595: E/AndroidRuntime(907): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
04-21 16:55:04.595: E/AndroidRuntime(907): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
04-21 16:55:04.595: E/AndroidRuntime(907): at dalvik.system.NativeStart.main(Native Method)
04-21 16:55:04.595: E/AndroidRuntime(907): Caused by: java.lang.IllegalAccessException: access to class not allowed
04-21 16:55:04.595: E/AndroidRuntime(907): at java.lang.Class.newInstanceImpl(Native Method)
04-21 16:55:04.595: E/AndroidRuntime(907): at java.lang.Class.newInstance(Class.java:1319)
04-21 16:55:04.595: E/AndroidRuntime(907): at android.app.Instrumentation.newActivity(Instrumentation.java:1023)
04-21 16:55:04.595: E/AndroidRuntime(907): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1871)
04-21 16:55:04.595: E/AndroidRuntime(907): ... 11 more
04-21 16:55:04.775: I/dalvikvm(907): threadid=3: reacting to signal 3
04-21 16:55:04.826: I/dalvikvm(907): Wrote stack traces to '/data/anr/traces.txt'
04-21 16:55:05.155: I/dalvikvm(907): threadid=3: reacting to signal 3
04-21 16:55:05.175: I/dalvikvm(907): Wrote stack traces to '/data/anr/traces.txt'
04-21 16:55:07.255: I/Process(907): Sending signal. PID: 907 SIG: 9
可能是什么问题？
答案 0 :(得分：5)
由于堆栈跟踪显示：
java.lang.IllegalAccessException: access to class not allowed
这意味着
class Home extends Activity {
应该是
public class Home extends Activity {
活动必须是public个类，否则Android将无法访问它们。
答案 1 :(得分：0)
您的代码存在两个问题。
1-制作课程public，以便您可以访问它。
2-你忘了添加
progress = (Button)this.findViewById(R.id.progress);
这就是你得到 nullPointer 的原因 现在，你很高兴去！