标签：android style blog http color java 使用 io
<application
android:name="com.example.applicationdemo.MyApplication"
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >其中MyApplication类就是我们自定义的一个类，继承自Application类public class MyApplication extends Application {
public String name;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Override
public void onCreate() {
// TODO Auto-generated method stub
super.onCreate();
}
}
public class MainActivity extends Activity {
private MyApplication application;
private Button btnName;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
application = (MyApplication) getApplication();
application.setName("YangLiang");
btnName = (Button) findViewById(R.id.btn_name);
btnName.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(MainActivity.this, ShowNameActivity.class);
startActivity(intent);
}
});
}
}MyApplication类public class MyApplication extends Application {
public String name;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Override
public void onCreate() {
// TODO Auto-generated method stub
super.onCreate();
}
}另一个activity，显示内容public class ShowNameActivity extends Activity {
private MyApplication app;
private TextView tv;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.showname);
app = (MyApplication) getApplication();
String name = app.getName();
tv = (TextView) findViewById(R.id.tv_showname);
tv.setText(name.toLowerCase());
}
}打开应用后，进入ShowNameActivity界面中，然后按home键进入后台，一段时间后，再次打开demo，就出现了空指针异常
tv.setText(name.toLowerCase());name在这个时候已经为空了
app = (MyApplication) getApplication(); String name = app.getName(); tv.setText(name.toLowerCase());上面的name就是空的，因此会出现空指针异常，也就是说，我们存储在application中的数据，有可能会因为程序运行在后台的时候导致application的销毁和重建进而导致数据的丢失，这对于程序来说是致命的，直接导致空指针异常的出现，程序崩溃。
Android应用之——不要将数据存储在Application类中,布布扣,bubuko.com
Android应用之——不要将数据存储在Application类中
标签：android style blog http color java 使用 io
原文地址：http://blog.csdn.net/csr_yang/article/details/38358171
