Java android.app.Application 无法转换为 android.app.Activity
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android.app.Application cannot be cast to android.app.Activity
提问by DomeWTF
I'm trying to change a LinearLayoutfrom another class, but when i run this code:
我正在尝试LinearLayout从另一个类更改 a ，但是当我运行此代码时：
public class IRC extends PircBot {
ArrayList<String> channels;
ArrayList<Integer> userCount;
ArrayList<String> topics;
LinearLayout channelLayout;
Context context;
public IRC(Context ctx) {
this.setName("xxxx");
channels = new ArrayList<String>();
userCount = new ArrayList<Integer>();
topics = new ArrayList<String>();
context = ctx;
channelLayout = (LinearLayout) ((Activity) context).findViewById(R.id.channels);
}
i get a ClassCastException
我得到一个 ClassCastException
context is the Main activity that extends Activitypassed with a getApplicationContext();
context 是Activity通过 getApplicationContext() 传递的 Main 活动；
LOGCAT
逻辑猫
05-08 17:53:55.102 3736-3799/g.d.allinonechat E/AndroidRuntime﹕ FATAL EXCEPTION: Thread-5357
java.lang.ClassCastException: android.app.Application cannot be cast to android.app.Activity
at g.d.xxx.IRC.<init>(IRC.java:34)
at g.d.xxx.MainActivity.run(MainActivity.java:49)
at java.lang.Thread.run(Thread.java:856)
采纳答案by codeMagic
You are passing the Application Contextnot the Activity Contextwith
您正在传递应用程序Context而不是Activity Context与
getApplicationContext();
Wherever you are passing it pass thisor ActivityName.thisinstead.
无论你在哪里通过它通过this或ActivityName.this相反。
Since you are trying to cast the Contextyou pass (Application not Activity as you thought) to an Activitywith
由于您正在尝试将Context您传递的（应用程序不是您认为的活动）转换为Activitywith
(Activity)
you get this exception because you can't cast the Application to Activitysince Application is not a sub-class of Activity.
您会收到此异常，因为您无法将 Application 强制转换为，Activity因为 Application 不是Activity.
回答by Gerrard
In my case, when I'm in an activity that extends from AppCompatActivity, it did not work(Activity) getApplicationContext (), I just putthisin its place.
就我而言，当我参与从 扩展的活动时AppCompatActivity，它不起作用(Activity) getApplicationContext ()，我只是将this其放在了它的位置。
回答by Nicolai Weitkemper
For me, removing android:name=".MainActivity"from <application …did the trick.
对我来说，除去android:name=".MainActivity"从<application …没有的伎俩。
回答by Aakash Sharma
You are getting this error because the parameter required is Activity and you are passing it the Application.
So, either you cast application to the Activity like: (Activity)getApplicationContext();Or you can just type the Activity like: MyActivity.this
您收到此错误是因为所需的参数是 Activity 并且您将其传递给应用程序。因此，您可以将应用程序转换为 Activity ，例如：(Activity)getApplicationContext();或者您可以键入 Activity ，例如：MyActivity.this
