Android_Mars学习笔记_S01_001activity初步

一、activity初步

1.程序启动会先读配置文件AndroidManifest.xml找activity

2.activity会在onCreate方法中读取activity_main.xml文件，加载内容,每个activity的配置文件都会在R.java中生成id

二、代码

1.AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>

<manifest xmlns:android="http://schemas.android.com/apk/res/android"

    package="com.tony.androidfirst"

    android:versionCode="1"

    android:versionName="1.0" >

    <uses-sdk

        android:minSdkVersion="8"

        android:targetSdkVersion="23" />

    <application

        android:allowBackup="true"

        android:icon="@drawable/ic_launcher"

        android:label="@string/app_name"

        android:theme="@style/AppTheme" >

        <activity

            android:name=".MainActivity"

            android:label="@string/app_name" >

            <intent-filter>

                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />

            </intent-filter>

        </activity>

    </application>

</manifest>

2.MainActivity.java

package com.tony.androidfirst;

import android.support.v7.app.ActionBarActivity;

import android.os.Bundle;

import android.view.Menu;

import android.view.MenuItem;

public class MainActivity extends ActionBarActivity {

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

    }

    @Override

    public boolean onCreateOptionsMenu(Menu menu) {

        // Inflate the menu; this adds items to the action bar if it is present.

        getMenuInflater().inflate(R.menu.main, menu);

        return true;

    }

    @Override

    public boolean onOptionsItemSelected(MenuItem item) {

        // Handle action bar item clicks here. The action bar will

        // automatically handle clicks on the Home/Up button, so long

        // as you specify a parent activity in AndroidManifest.xml.

        int id = item.getItemId();

        if (id == R.id.action_settings) {

            return true;

        }

        return super.onOptionsItemSelected(item);

    }

}

3.activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:tools="http://schemas.android.com/tools"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    android:paddingBottom="@dimen/activity_vertical_margin"

    android:paddingLeft="@dimen/activity_horizontal_margin"

    android:paddingRight="@dimen/activity_horizontal_margin"

    android:paddingTop="@dimen/activity_vertical_margin"

    tools:context="com.tony.androidfirst.MainActivity" >

    <TextView

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:textSize="80sp"

        android:background="#FF0000"

        android:text="Hello android" />

</RelativeLayout>

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Android_Mars学习笔记_S01_001activity初步

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