我的应用程序崩溃，我认为这是由于SharedPreferencesManager prefManager = SharedPreferencesManager.getInstance(this);全局存储在Content类中。但是，如果我把它拿出来，那么我就不能在switch语句中进一步使用prefManager。
我想使用prefManager中的点击次数来确定我的switch语句。我怎么能绕过这个？
public class Content extends AppCompatActivity {
Button selectAnotherButton;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_content);
final SharedPreferencesManager prefManager = SharedPreferencesManager.getInstance(this);
selectAnotherButton = findViewById(R.id.button_select_another);
selectAnotherButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
prefManager.increaseClickCount();
for (int i = 0; i <= 100; i+=2) {
ShowRewardDialog();
}
}
});
private void ShowRewardDialog() {
String message = "";
//show dialog
// set text based on an if statement you need to create
switch (SharedPreferencesManager.getInstance(this).increaseClickCount()){
case 2 :
message = "You are rewarded with a video";
break;
case 4 :
message = "You are rewarded with a the yellow smiley face in the homepage";
break;
case 6 :
message = "You are rewarded with a video";
break;
case 8 :
message = "You are rewarded with a the green smiley face in the homepage";
break;
case 10 :
message = "You are rewarded with a video";
break;
case 12 :
message = "You are rewarded with a the red smiley face in the homepage";
break;
case 14 :
message = "You are rewarded with a video";
break;
default :
message="";
}
// custom dialog
final Dialog dialog = new Dialog(context);
dialog.setContentView(R.layout.custom_dialog);
SpannableString title = new SpannableString("YOU GAINED A REWARD");
title.setSpan(new ForegroundColorSpan(context.getResources().getColor(R.color.purple))
, 0, title.length(), Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
// set the custom dialog components - text, image and button
TextView text = dialog.findViewById(R.id.dialog_text);
dialog.setTitle(title);
text.setText(message);
Button dialogButton = dialog.findViewById(R.id.dialog_button_OK);
// if button is clicked, close the custom dialog
dialogButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
dialog.dismiss();
}
});
dialog.show();
}
}
堆栈追踪：
06-14 21:57:39.420 15488-15488/com.mima.chilltime E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.mima.chilltime, PID: 15488
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.mima.chilltime/com.mima.chilltime.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.Context android.content.Context.getApplicationContext()' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2989)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3260)
at android.app.ActivityThread.access$1000(ActivityThread.java:218)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1734)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:6934)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1404)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1199)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.Context android.content.Context.getApplicationContext()' on a null object reference
at android.content.ContextWrapper.getApplicationContext(ContextWrapper.java:111)
at com.mima.chilltime.SharedPreferencesManager.<init>(SharedPreferencesManager.java:19)
at com.mima.chilltime.SharedPreferencesManager.getInstance(SharedPreferencesManager.java:25)
at com.mima.chilltime.MainActivity.<init>(MainActivity.java:25)
at java.lang.reflect.Constructor.newInstance(Native Method)
at java.lang.Class.newInstance(Class.java:1690)
at android.app.Instrumentation.newActivity(Instrumentation.java:1094)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2979)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3260)
at android.app.ActivityThread.access$1000(ActivityThread.java:218)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1734)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:6934)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1404)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1199)
答案 0 :(得分：1)
尝试使用
SharedPreferencesManager.getInstance(getApplicationContext());
而不是使用this
答案 1 :(得分：0)
在SharedPreferencesManager.getInstance(this); .... this中指特定活动（即不全局）（即其生命周期与当前直接相关 context）。
另一方面，如果您明确需要引用应用程序的全局状态，则可以使用ApplicationContext。
来自Android Documentation（我的重点）：
public Context getApplicationContext()返回单个全局应用程序对象的上下文 目前的过程。这通常只应在需要的时候使用 生命周期与当前上下文分开的上下文，即 与流程的生命周期相关，而非当前组件。
所以改为：
SharedPreferencesManager prefManager = SharedPreferencesManager.getInstance(getApplicationContext());