Android学习笔记（二）

最新推荐文章于 2025-08-23 10:36:55 发布

chandlersong

最新推荐文章于 2025-08-23 10:36:55 发布

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分类专栏： Android 文章标签： android ui processing import resources database

本文链接：https://blog.youkuaiyun.com/chandlersong/article/details/4287344

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本文详细介绍了Android中Activity的生命周期，包括不同状态如Active、Paused、Stopped等的概念，并通过具体的方法如onCreate、onStart、onResume等展示了Activity从启动到销毁的全过程。此外，还提到了几种特定类型的Activity。

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activity的生命周期。

这里也是主要是几个概念为主。

首先是在Manifest.xml中的配置。其中比较特别的是<intent-filter>这个标签，不过这是以后讲的东西，所以这里也没讲太多。

其次是Activity Stacks，其时Last-in-first-out也就是先进先出的模式。

Activity States

Active：和用户交互的activity，通俗点就是当前你看到的页面。

Paused：能够看得见，但是不发生交互的activity。比方说不是全屏显示的失去了焦点。

Stopped：不可见，但是还在stacks中的。

Inactive：移出stacks的

Monitoring State Changes和生命周期

package com.paad.myapplication;
   import android.app.Activity;
    import android.os.Bundle;
    public class MyActivity extends Activity {
    // Called at the start of the full lifetime.
    @Override
    public void onCreate(Bundle icicle) {
        super.onCreate(icicle);
        // Initialize activity.
     }
     // Called after onCreate has finished, use to restore UI state
    @Override
    public void onRestoreInstanceState(Bundle savedInstanceState) {
            super.onRestoreInstanceState(savedInstanceState);
            // Restore UI state from the savedInstanceState.
            // This bundle has also been passed to onCreate.
       }
    // Called before subsequent visible lifetimes
    // for an activity process.
    @Override
    public void onRestart(){
        super.onRestart();
        // Load changes knowing that the activity has already
        // been visible within this process.
     }
    // Called at the start of the visible lifetime.
    @Override
     public void onStart(){
        super.onStart();
        // Apply any required UI change now that the Activity is visible.
     }
     // Called at the start of the active lifetime.
    @Override
    public void onResume(){
            super.onResume();
            // Resume any paused UI updates, threads, or processes required
            // by the activity but suspended when it was inactive.
    }
        // Called to save UI state changes at the
        // end of the active lifecycle.
    @Override
    public void onSaveInstanceState(Bundle savedInstanceState) {
        // Save UI state changes to the savedInstanceState.
         // This bundle will be passed to onCreate if the process is
            // killed and restarted.
                super.onSaveInstanceState(savedInstanceState);
        }
      // Called at the end of the active lifetime.
     @Override
     public void onPause(){
            // Suspend UI updates, threads, or CPU intensive processes
            // that don’t need to be updated when the Activity isn’t
            // the active foreground activity.
        super.onPause();
    }
   // Called at the end of the visible lifetime.
    @Override
    public void onStop(){
        // Suspend remaining UI updates, threads, or processing
        // that aren’t required when the Activity isn’t visible.
        // Persist all edits or state changes
        // as after this call the process is likely to be killed.
        super.onStop();
    }
    // Called at the end of the full lifetime.
    @Override
    public void onDestroy(){
        // Clean up any resources including ending threads,
        // closing database connections etc.
        super.onDestroy();
    }
}

书中有张图。比较清晰的解释了他们之间的逻辑关系。有兴趣的可以去看一下。

还有种记忆方法就是

The Full Lifetime：onCreate和onDestroy 整个程序

The Visible Lifetime：onStart和nStop 进入Active

The Active Lifetime：onResume和onPause ，获得和失去焦点。

Android Activity Classes

MapActivity，ListActivity，ExpandableListActivity，ActivityGroup