Android开发学习---sharedpreference的使用

在前面文章中,为了使数据回显,使用的技术思路是,首先,将数据持久化写到ROM或者SDCard中,其中name和password以":"分隔;然后,将数据记取出来,再用split方法将数据切割,分割后的数据再set到输入框中.整个过程可谓是相当麻烦,一不小心就会报空指针的错误,而且很容易忘记写参数.下面将学习一个叫SharedPreference东西.SharedPreference主要用来保存参数.

1.效果:

2.实现代码

package com.amos.sharedpreference;

import android.app.Activity;
import android.content.SharedPreferences;
import android.content.SharedPreferences.Editor;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.EditText;

public class MainActivity extends Activity implements OnClickListener {
    String tag = "MainActivity";
    EditText et_name;// 用户名
    EditText et_password;// 密码
    Button bt_login;// 登录按钮
    CheckBox cb_password;// 单选框

    // 用来保存参数的接口
    SharedPreferences sharedPreference;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        // 初始化
        et_name = (EditText) this.findViewById(R.id.et_name);
        et_password = (EditText) this.findViewById(R.id.et_password);
        bt_login = (Button) this.findViewById(R.id.bt_login);
        cb_password = (CheckBox) this.findViewById(R.id.cb_password);

        // 初始化参数配置
        sharedPreference=this.getSharedPreferences("spconfig", MODE_PRIVATE);
        if(sharedPreference.getBoolean("issetup", false)){
            et_name.setText(sharedPreference.getString("name", ""));
            et_password.setText(sharedPreference.getString("password", ""));
        }
        
        
        // 注册监听事件
        bt_login.setOnClickListener(this);

    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
        case R.id.bt_login:
            String name = et_name.getText().toString().trim();
            String password = et_password.getText().toString().trim();
            System.out.println("name:"+name);
            System.out.println("password:"+password);
            // 定义用来保存参数的接口
            Editor edit = sharedPreference.edit();
            edit.putString("name", name);
            edit.putString("password", password);
            edit.putBoolean("issetup", true);
            //清空编辑器
            //edit.clear();
            
            // 当有两个编辑器(Editor)进行编辑同一个sharedPreference时,最后一个提交的将会生效
            edit.commit();
            
        default:
            break;
        }

    }

}

sharedpreference的使用是相当方便,这里同样会将用户名密码保存下来,但这里不同点在于,通过sharedPreference会生成规整的xml的文件,这里主要用到的是Edit类中的方法去put值到相应的位置.一般情况下其它配置也是会保存到sharedPreference中,如setting:

 3.补充

1).使用openFileInput('...')读取数据.

前面文章中将密码写到rom文件中主要采用的是openFileOutput('XXX/xxx').

这里同样可以类似的通过openFileInput('xx/xxx')进行读取文件.比较简单,这里不再举例.

2).使用命令生成sdcard

t-bundle-linux-x86_64-20131030/sdk/tools$ ./mksdcard 20
mksdcard: create a blank FAT32 image to be used with the Android emulator
usage: mksdcard [-l label] <size> <file>

  if <size> is a simple integer, it specifies a size in bytes
  if <size> is an integer followed by 'K', it specifies a size in KiB
  if <size> is an integer followed by 'M', it specifies a size in MiB
  if <size> is an integer followed by 'G', it specifies a size in GiB

Minimum size is 9M. The Android emulator cannot use smaller images.
Maximum size is 1099511627264 bytes, 1073741823K, 1048575M or 1023G
amosli@amosli-pc:/media/f91a4cca-0b96-4c30-b140-7918a196de3e/amosli/java/soft/adt-bundle-linux-x86_64-20131030/sdk/tools$ 

 3).更新ADT(android development tools )

方法一:将 https://dl-ssl.google.com/android/eclipse/ 链接加入到, Help > Install New Software > add url

方法二:直接下载zip包ADT-22.6.3.zip　(https://dl.google.com/android/ADT-22.6.3.zip),不用解压.步骤与add url类似,官方介绍如下.

1. Download the ADT Plugin zip file (do not unpack it):

   Package	Size	MD5 Checksum
   ADT-22.6.3.zip	14590813 bytes	3982259fd2cc81e53bbbe05dcd6529a7

2. Start Eclipse, then select Help > Install New Software.
3. Click Add, in the top-right corner.
4. In the Add Repository dialog, click Archive.
5. Select the downloaded ADT-22.6.3.zip file and click OK.
6. Enter "ADT Plugin" for the name and click OK.
7. In the Available Software dialog, select the checkbox next to Developer Tools and click Next.
8. In the next window, you'll see a list of the tools to be downloaded. Click Next.
9. Read and accept the license agreements, then click Finish.

也可以直接从百度网盘中下载(推荐):http://pan.baidu.com/s/1i3rAc2D