我是一名Android编程的初学者,不幸的是,我遇到了一个问题 :)
我的游戏中有一个名为writeSettings()的方法,在其中我试图保存一些变量,以便在使用readSettings()方法加载上一次游戏时使用。这些参数包括first(second)PlayerName, first(second)PlayerScore等。 我试图使用SharedPreferences来保存它们,但是当启动程序时,会出现“强制关闭”对话框。
SharedPreferences preferences = getPreferences(MODE_PRIVATE); //Global variable
private void writeSettings() {
SharedPreferences.Editor editor = preferences.edit();
editor.putInt("timeSave", time);
editor.putString("firstPlayerNameSave", firstPlayerNameTextView.getText().toString());
editor.putString("secondPlayerNameSave", secondPlayerNameTextView.getText().toString());
editor.putString("firstPlayerScoreSave", firstPlayerScoreTextView.getText().toString());
editor.putString("secondPlayerScoreSave", secondPlayerScoreTextView.getText().toString());
editor.putInt("nowPlayerSave", nowPlayer);
editor.commit();
}
private void readSettings() {
//"time" parameter program reads in another method
firstPlayerNameTextView.setText(preferences.getString("firstPlayerNameSave", ""));
secondPlayerNameTextView.setText(preferences.getString("secondPlayerNameSave", ""));
firstPlayerScoreTextView.setText(preferences.getString("firstPlayerScoreSave", ""));
secondPlayerScoreTextView.setText(preferences.getString("secondPlayerScoreSave", ""));
nowPlayer = preferences.getInt("nowPlayerSave", -1);
}
我不知道我做错了什么,但我能看出问题出现在writeSettings()的第一个条目。很抱歉我的英文表达不好。
更新:
12-23 16:23:31.334: ERROR/AndroidRuntime(410): Uncaught handler: thread main exiting due to uncaught exception
12-23 16:23:31.520: ERROR/AndroidRuntime(410): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.game/com.game.Game}: java.lang.NullPointerException
12-23 16:23:31.520: ERROR/AndroidRuntime(410): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2417)
12-23 16:23:31.520: ERROR/AndroidRuntime(410): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2512)
12-23 16:23:31.520: ERROR/AndroidRuntime(410): at android.app.ActivityThread.access$2200(ActivityThread.java:119)
12-23 16:23:31.520: ERROR/AndroidRuntime(410): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1863)
12-23 16:23:31.520: ERROR/AndroidRuntime(410): at android.os.Handler.dispatchMessage(Handler.java:99)
12-23 16:23:31.520: ERROR/AndroidRuntime(410): at android.os.Looper.loop(Looper.java:123)
12-23 16:23:31.520: ERROR/AndroidRuntime(410): at android.app.ActivityThread.main(ActivityThread.java:4363)
12-23 16:23:31.520: ERROR/AndroidRuntime(410): at java.lang.reflect.Method.invokeNative(Native Method)
12-23 16:23:31.520: ERROR/AndroidRuntime(410): at java.lang.reflect.Method.invoke(Method.java:521)
12-23 16:23:31.520: ERROR/AndroidRuntime(410): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860)
12-23 16:23:31.520: ERROR/AndroidRuntime(410): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
12-23 16:23:31.520: ERROR/AndroidRuntime(410): at dalvik.system.NativeStart.main(Native Method)
12-23 16:23:31.520: ERROR/AndroidRuntime(410): Caused by: java.lang.NullPointerException
12-23 16:23:31.520: ERROR/AndroidRuntime(410): at android.content.ContextWrapper.getPackageName(ContextWrapper.java:120)
12-23 16:23:31.520: ERROR/AndroidRuntime(410): at android.app.Activity.getLocalClassName(Activity.java:3410)
12-23 16:23:31.520: ERROR/AndroidRuntime(410): at android.app.Activity.getPreferences(Activity.java:3444)
12-23 16:23:31.520: ERROR/AndroidRuntime(410): at com.game.Game.<init>(Game.java:69)
12-23 16:23:31.520: ERROR/AndroidRuntime(410): at java.lang.Class.newInstanceImpl(Native Method)
12-23 16:23:31.520: ERROR/AndroidRuntime(410): at java.lang.Class.newInstance(Class.java:1479)
12-23 16:23:31.520: ERROR/AndroidRuntime(410): at android.app.Instrumentation.newActivity(Instrumentation.java:1021)
12-23 16:23:31.520: ERROR/AndroidRuntime(410): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2409)
12-23 16:23:31.520: ERROR/AndroidRuntime(410): ... 11 more
Game.java:69 代码中的 SharedPreferences preferences = getPreferences(MODE_PRIVATE);
是使用 MODE_PRIVATE 获取该 Activity 的 SharedPreferences 对象。