本文介绍了如何传递上下文?的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我想将主要活动的上下文传递给另一个类,以创建Toast.
I want to pass the context of the main activity to another class in order to create a Toast.
我的主要活动是调用一个将删除文件的类.如果文件不存在,则删除文件的类将调用Toast.
My main activity calls a class that will delete a file.The class that deletes files will call a toast if the file does not exist.
这是我的代码:
public class MyActivity extends AppCompatActivity
{
public void onCreate(Bundle savedInstanceState)
{
// create a file
Button buttoncreate = (Button)findViewById(R.id.create_button);
Button buttondelete = (Button)findViewById(R.id.delete_button);
...
buttondelete.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
new DeleteFile();
}
});
}
public class DeleteFile extends AsyncTask {
@Override
public Object doInBackground(Object[] params) {
File root = android.os.Environment.getExternalStorageDirectory();
File dir = new File(root.getAbsolutePath() + "/mydir");
if (!(dir.exists())) {
CharSequence text = "Files do not exist!";
int duration = Toast.LENGTH_SHORT;
Toast toast = Toast.makeText(getApplicationContext(), text, duration);
toast.show();
} else {
File file;
file = new File(dir, "mydata.bmp");
file.delete();
}
return(1);
}
}
推荐答案
首先,您需要使用静态变量在应用程序类中声明全局变量,
像这样
First thing, you need Static Variable to declare global variable in Application Class,
like this
class GlobalClass extends Application {
public static Context context;
@Override
public void onCreate() {
super.onCreate();
context = getApplicationContext();
}
}
您需要在应用程序标记内的AndroidManifest.xml中设置此类
像这样:
second you need set this class in AndroidManifest.xml inside application tag
like this:
<application
android:name=".GlobalClass"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@android:style/Theme.Black.NoTitleBar" >
然后,在需要访问此数据的任何地方,均可通过以下方式获取Application对象:
then whereever you need to access this data, get Application object by:
Toast toast = Toast.makeText(GlobalClass.context, text, duration);
toast.show();
这篇关于如何传递上下文?的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持!