现在不管什么APP都有个头像，如果你看见没有头像的APP就会感觉非常奇怪，以前头像都是方的，后来就变成圆的，我估计在过个几年就得来个五角星形状的头像，下面我把更换头像的代码写来：

<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"
    tools:context=".MainActivity" >

    <ImageView
        android:id="@+id/iv_head"
        android:layout_width="200dip"
        android:layout_height="200dip"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="210dip"
        android:src=http://www.mamicode.com/"@drawable/ic_launcher" />>
首先我定义了一个非常简单的XML布局，里面两个Button，一个ImageView用来显示头像：
下面我来看看MainActivity代码：
package com.example.changhead;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;


import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.provider.MediaStore;
import android.annotation.SuppressLint;
import android.app.Activity;
import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageView;

@SuppressLint("SdCardPath")
public class MainActivity extends Activity implements OnClickListener {
	private ImageView ivHead;//头像显示
	private Button btnTakephoto;//拍照
	private Button btnPhotos;//相册
	private Bitmap head;//头像Bitmap
	private static String path="/sdcard/myHead/";//sd路径

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		initView();
	}

	private void initView() {
		//初始化控件
		btnPhotos = (Button) findViewById(R.id.btn_photos);
		btnTakephoto = (Button) findViewById(R.id.btn_takephoto);
		btnPhotos.setOnClickListener(this);
		btnTakephoto.setOnClickListener(this);
		ivHead = (ImageView) findViewById(R.id.iv_head);
		Bitmap bt = BitmapFactory.decodeFile(path + "head.jpg");//从Sd中找头像，转换成Bitmap
		if(bt!=null){
			@SuppressWarnings("deprecation")
			Drawable drawable = new BitmapDrawable(bt);//转换成drawable
			ivHead.setImageDrawable(drawable);
		}else{
			/**
			 *	如果SD里面没有则需要从服务器取头像，取回来的头像再保存在SD中
			 * 
			 */
		}
		
		
	
	}

	@Override
	public void onClick(View v) {
		switch (v.getId()) {
		case R.id.btn_photos://从相册里面取照片
			Intent intent1 = new Intent(Intent.ACTION_PICK, null);
			intent1.setDataAndType(MediaStore.Images.Media.EXTERNAL_CONTENT_URI, "image/*");
			startActivityForResult(intent1, 1);
			break;
		case R.id.btn_takephoto://调用相机拍照
			Intent intent2 = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
			intent2.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(new File(Environment.getExternalStorageDirectory(),
							"head.jpg")));
			startActivityForResult(intent2, 2);//采用ForResult打开
			break;
		default:
			break;
		}
	}
	protected void onActivityResult(int requestCode, int resultCode, Intent data) {
		switch (requestCode) {
		case 1:
			if (resultCode == RESULT_OK) {
				cropPhoto(data.getData());//裁剪图片
			}

			break;
		case 2:
			if (resultCode == RESULT_OK) {
				File temp = new File(Environment.getExternalStorageDirectory()
						+ "/head.jpg");
				cropPhoto(Uri.fromFile(temp));//裁剪图片
			}

			break;
		case 3:
			if (data != null) {
				Bundle extras = data.getExtras();
				head = extras.getParcelable("data");
				if(head!=null){
					/**
					 * 上传服务器代码
					 */
					setPicToView(head);//保存在SD卡中
					ivHead.setImageBitmap(head);//用ImageView显示出来
				}
			}
			break;
		default:
			break;

		}
		super.onActivityResult(requestCode, resultCode, data);
	};
	/**
	 * 调用系统的裁剪
	 * @param uri
	 */
	public void cropPhoto(Uri uri) {
		Intent intent = new Intent("com.android.camera.action.CROP");
		intent.setDataAndType(uri, "image/*");
		intent.putExtra("crop", "true");
		 // aspectX aspectY 是宽高的比例
		intent.putExtra("aspectX", 1);
		intent.putExtra("aspectY", 1);
		// outputX outputY 是裁剪图片宽高
		intent.putExtra("outputX", 150);
		intent.putExtra("outputY", 150);
		intent.putExtra("return-data", true);
		startActivityForResult(intent, 3);
	}
	private void setPicToView(Bitmap mBitmap) {
		 String sdStatus = Environment.getExternalStorageState();  
        if (!sdStatus.equals(Environment.MEDIA_MOUNTED)) { // 检测sd是否可用  
               return;  
           }  
		FileOutputStream b = null;
		File file = new File(path);
		file.mkdirs();// 创建文件夹
		String fileName =path + "head.jpg";//图片名字
		try {
			b = new FileOutputStream(fileName);
			mBitmap.compress(Bitmap.CompressFormat.JPEG, 100, b);// 把数据写入文件
			
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} finally {
			try {
				//关闭流
				b.flush();
				b.close();
			} catch (IOException e) {
				e.printStackTrace();
			}

		}
}
}
上面的注释已经很详细了，就这些
对了不要忘记加权限：
<uses-permission android:name="android.permission.CAMERA"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/>  

源码下载



Android更换头像功能实现