Activity生命周期以及Intent两种画面跳转方式

Activity的生命周期

onCreate()；创建

onStart()；运行

onResume()；获取焦点

onPasue()；失去焦点

onStop()；暂停

onDestroy()；销毁

onRestart()；

–活动状态(Active/Running) Activity处于界面最顶端，获取焦点

–暂停状态(Paused) Activity失去焦点，但对用户可见

–停止状态(Stopped) Activity被完全遮挡，但保留所有状态和成员信息

–非活动状态(Killed)Activity被停止

什么是Intent

Intent可以理解为信使(意图)

由Intent来协助完成Android各个组件之间的通讯

Intent 包括两种跳转方式

1.无返回结果的跳转方式：

import android.app.Activity;import android.content.Intent;import android.os.Bundle;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;public class FirstActivity extends Activity{private Button btn;@Overrideprotected void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.activity_first);    btn = (Button) findViewById(R.id.button1);    btn.setOnClickListener(new OnClickListener() {        @Override        public void onClick(View v) {            Intent intent = new Intent(FirstActivity.this,SActivity.class);            startActivity(intent);        }    });}}

2.有返回结果的页面跳转

第一个画面public class FirstActivity extends Activity{    private Button btn;    private TextView tv;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_first);        tv = (TextView) findViewById(R.id.mTextView);        btn = (Button) findViewById(R.id.button2);        btn.setOnClickListener(new OnClickListener() {            @Override            public void onClick(View v) {                Intent intent = new Intent(FirstActivity.this,SActivity.class);                startActivityForResult(intent, 1);            }        });    }    @Override    protected void onActivityResult(int requestCode, int resultCode, Intent data) {        super.onActivityResult(requestCode, resultCode, data);        if (requestCode==1 && resultCode ==2) {            String context = data.getStringExtra("data");            tv.setText(context);        }    }}第二个跳转画面public class SActivity extends Activity{    private Button btn;    private String datas = "hello word";    @Override    protected void onCreate(Bundle savedInstanceState) {        // TODO 自动生成的方法存根        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_seconed);        btn = (Button) findViewById(R.id.button3);        btn.setOnClickListener(new OnClickListener() {            @Override            public void onClick(View v) {                Intent data = new Intent();                data.putExtra("data", datas);                setResult(2, data);                finish();            }        });    }}<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical" >    <Button        android:id="@+id/button1"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="启动第一个页面" />    <Button        android:id="@+id/button2"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="启动第二个页面" />    <TextView         android:id="@+id/mTextView"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="显示返回结果"        /></LinearLayout><?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical" >    <Button        android:id="@+id/button3"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="点击返回" /></LinearLayout>