Android 点击关闭所有activity

有两种方式一种是用广播点击关闭所有打开activity,点击用广播关闭activity的例子网上比较多，在这里就不做介绍了。我是用一个list集合控制activity的，每当打开一个activity写的全局类，就记录一个，然后在最后把记录的activity,   finis掉就行了。
[b]My_Aplication(要在清单文件的apllcation里面注册)[/b]

import android.app.Activity;
import android.app.Application;

import java.util.ArrayList;
import java.util.List;

public class My_Aplication extends Application{
public List<Activity> list;

@Override
public void onCreate() {
super.onCreate();
list=new ArrayList<Activity>();
}
public void dateActivity(Activity activity){
list.add(activity);
}
}

MainActivity（下面打开的Activity,都会通过全局类，记录到List集合里面）import android.app.Activity;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import java.util.List;

public class MainActivity extends AppCompatActivity {
private List<Activity> list;
private Button mBtn;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
((My_Aplication)getApplicationContext()).dateActivity(MainActivity.this);
mBtn= (Button) findViewById(R.id.mBtn);
}

public void onClick(View view) {
startActivity(new Intent(MainActivity.this,B.class));
}
}Bimport android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
public class B extends Activity{
private Button mBtn;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.b);
((My_Aplication)getApplicationContext()).dateActivity(B.this);
mBtn= (Button) findViewById(R.id.mBtn);
}

public void onClick(View view) {
startActivity(new Intent(B.this,C.class));
}
}C（在最终的方法里面，从list里面找到每一个打开过的activity,赋值给activity,然后在把activity关掉）import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import java.util.List;

public class C extends Activity{
private List<Activity> list;
private Button mBtn;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.c);
list=((My_Aplication)getApplicationContext()).list;
mBtn=(Button) findViewById(R.id.mBtn);
}

public void onClick(View view) {
for (int i=0;i<list.size();i++){
//记录打开的每个activity
Activity activity=list.get(i);
activity.finish();
}
finish();
}
}activity别忘了注册。。。。。