oncreate | 易学教程

Error: SPAN_EXCLUSIVE_EXCLUSIVE spans cannot have a zero length

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I got a problem with my android app. I got a button and and event associated , but when I click the first time an error appears "spans cannot have zero lenght". . But when I click the second time, the event onclick runs well.. look at my java code: public class MainActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); final Button selectAltitude = (Button) findViewById(R.id.buttonAltitude1); final Button selectAltitude2 = (Button) findViewById(R.id.buttonAltitude2); selectAltitude2

Android 第六课——Activity高级

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Activity 生命周期：生命周期7个方法的调用时机： 1）onCreate：第一次创建这个Activity时，也就是系统中没有缓存当前的Activity时，这个方法首先被调用。调用之后这个Activity就会被压入所谓的Android Task栈中缓存起来，下次用时出栈就可以。所以，为了更加节约资源，我们一般把Activity所对应的layout中拥有的组件首先使用private作为这个Activity的私有成员，然后在onCreate方法中初始化，这样只要在Activity创建的时候，初始化一次组件就够了。 2）onstart：当这个Activity成为用户可见状态时，也就是在手机界面上正确显示的时候这个方法会被调用。所以，如果一个Activity之前已经创建好了，下次再次调用时（比如返回按钮）就会从Task栈中获取直接返回给用户，那么就不会再调用onCreate了，而是先调用onRestart,然后等到用户可见状态时调用onStart。 3）onResume：当这个Activity成为用户可见状态而且用户可以获取焦点时，也就是在onStart之后，当这个视图可以与用户交互时这个方法会被调用。这个方法调用完成之后，整个Activity就是处于运行状态了。 4）onPause：当一个Activity正在使用，这时另一个Activity开始启动

Why do OnCreate should be called only once on the start of Activity?

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问题 I would like to know, why OnCreate() is called only once at the start of an activity? Can we call OnCreate() more than once in the same activity? If yes, than how can we call it? can anyone give an example? Thanks a lot!!! 回答1: Why would you want to called it again? unless the activity is reconstructed, which is called by system. You cannot call OnCreate manually , it is the same reason why you won't call setContentView() twice. as docs: onCreate(Bundle) is where you initialize your activity.

Can you please explain onCreate and Bundles?

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问题 I have been looking it up and I just cant seem to wrap myself around the onCreate and Bundles. I understand that the onCreate is called when the program starts but its how the Bundles get passed around and how they are pertinent. Can anyone try to put this into plain english because I cant seem to find it well described. Thanks 回答1: The Bundle in the onCreate method should hold the state of you activity before it was killed. Simple example, when you change the orientation of your device your

Should I restore savedinstancestate in onCreate or in onRestoreInstanceState?

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I have an activity that starts some other activities for results, so when the result comes back, the activity may or may not have been destroyed and recreated. I have overridden onSaveInstanceState so as to add the data that needs to be preserved and restored. When the activity gets destroyed and recreated, onCreate is passed the savedInstanceState bundle; but also onRestoreInstanceState() is called and passed the same bundle. So where should I put the code that extracts the data from the bundle and restores the state? In onCreate or in onRestoreInstanceState? Is the latter guaranteed to be

AlertDialog with spinner on start of activity

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I am trying to create an AlertDialog with a spinner on the start of an activity. I have the following code within the activity's onCreate() method. AlertDialog.Builder builder = new AlertDialog.Builder(this); AlertDialog alertDialog; Context mContext = getApplicationContext(); LayoutInflater inflater = (LayoutInflater) mContext.getSystemService(LAYOUT_INFLATER_SERVICE); View layout = inflater.inflate(R.layout.custom_dialog, (ViewGroup) findViewById(R.id.layout_root)); Spinner spinner = (Spinner) layout.findViewById(R.id.spinner); ArrayAdapter<CharSequence> adapter = ArrayAdapter

requestFeature() must be called before adding content error on super.onCreate

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问题 I have an abstract class extending ActionBarActivity . In the onCreate , I have: @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); supportRequestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS); ... } The app crashes due to the requestFeature() before content error, specifically on the line super.onCreate(savedInstanceState) . After reading some of the similar posts, I came up with this solution: @Override protected void onCreate(Bundle

After the rotate, onCreate() Fragment is called before onCreate() FragmentActivity

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问题 I'm using FragmentActivity and Fragments. When the application starts: FragmentActivity onCreate() <------ FragmentActivity onStart() FragmentActivity onResume() Fragment onAttach() Fragment onCreate() <------ Fragment onCreateView() Fragment onActivityCreated() Fragment onStart() Fragment onResume() Everything is OK, FragmentActivity onCreate() is called before Fragment onCreate(). And when I rotate: Fragment onPause() FragmentActivity onPause() Fragment onStop() FragmentActivity onStop()

How do I instantiate a class in android which is also an activity?

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问题 In android, how can I create a constructor for a class which is also an Activity ? My problem is, I want to have two activity classes (estimateFare and Mapping) which both send data to a an activity class ( CalculateFare ). Mapping takes the data from real time network info, whereas estimateFare takes data from user input. I want CalculateFare to be able to use the data from either class to perform the calculation, although I have run into trouble with the onCreate method and the constructor

Can I use setContentView outside the oncreate method?

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I have seen many people telling that you can set setContentView outside the oncreate method, but I didn't find anywhere an example. Now when I try to use setContentView, my app just crashes. Here is my source code: AlarmActivity.java: package com.alarm.example; import android.app.Activity; import android.os.Bundle; import android.view.View; import android.view.ViewGroup.LayoutParams; import android.widget.Button; import android.widget.RelativeLayout; public class AlarmActivity extends Activity{ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState);