简单登录案例（SharedPreferences存储账户信息）&联网请求图片并下载到SD卡（文件外部存储）_移动开发

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简单登录案例（SharedPreferences存储账户信息）&联网请求图片并下载到SD卡（文件外部存储）

2016/8/17 5:33:02 llfy 程序员俱乐部我要评论(0)

摘要：新人刚学习Android两周，写一个随笔算是对两周学习成果的巩固，不足之处欢迎各位建议和完善。这次写的是一个简单登录案例，大概功能如下：注册的账户信息用SharedPreferences存储；登录成功后跳转到成功页面，在成功页面联网请求图片并写入到外部存储；然后读出显示在成功页面；注册xml代码：1<?xmlversion="1.0"encoding="utf-8"?>2<manifestxmlns:android="http://schemas.android
标签：图片文件下载 Preference SharedPreferences

　　新人刚学习Android两周，写一个随笔算是对两周学习成果的巩固，不足之处欢迎各位建议和完善。

　　这次写的是一个简单登录案例，大概功能如下：

　　　　注册的账户信息用SharedPreferences存储；

　　　　登录成功后跳转到成功页面，在成功页面联网请求图片并写入到外部存储；

　　　　然后读出显示在成功页面；

注册xml代码：

 1 <?xml version="1.0" encoding="utf-8"?>
 2 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
 3     package="com.qf.login"
 4     android:versionCode="1"
 5     android:versionName="1.0" >
 6 
 7     <uses-sdk
 8         android:minSdkVersion="14"
 9         android:targetSdkVersion="21" />
10     <!--联网权限  -->
11     <uses-permission android:name="android.permission.INTERNET"/>
12     <!--在SD卡中创建与删除文件权限  -->
13     <uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/>
14     <!--向SD卡写入数据权限  -->
15     <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
16 
17     <application
18         android:allowBackup="true"
19         android:icon="@drawable/ic_launcher"
20         android:label="@string/app_name"
21         android:theme="@style/AppTheme" >
22         <activity
23             android:name=".MainActivity"
24             android:label="@string/app_name" >
25             <intent-filter>
26                 <action android:name="android.intent.action.MAIN" />
27 
28                 <category android:name="android.intent.category.LAUNCHER" />
29             </intent-filter>
30         </activity>
31         <activity 
32             android:name=".Register"
33             ></activity>
34         <activity 
35             android:name=".SuccessLogin"
36             ></activity>
37     </application>
38 
39 </manifest>

MainActivity:

 1 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 2     xmlns:tools="http://schemas.android.com/tools"
 3     android:layout_width="match_parent"
 4     android:layout_height="match_parent"
 5     android:orientation="vertical" >
 6 
 7     <LinearLayout
 8         android:layout_width="match_parent"
 9         android:layout_height="wrap_content"
10         android:orientation="horizontal"
11         android:paddingTop="50dp" >
12 
13         <TextView
14             android:layout_width="0dp"
15             android:layout_height="wrap_content"
16             android:layout_weight="1"
17             android:gravity="center_horizontal"
18             android:text="账号" />
19 
20         <EditText
21             android:id="@+id/et1"
22             android:layout_width="0dp"
23             android:layout_height="wrap_content"
24             android:layout_marginRight="5dp"
25             android:layout_weight="4"
26             android:background="@drawable/app_pref_bg" />
27     </LinearLayout>
28 
29     <LinearLayout
30         android:layout_width="match_parent"
31         android:layout_height="wrap_content"
32         android:layout_marginTop="10dp"
33         android:orientation="horizontal" >
34 
35         <TextView
36             android:layout_width="0dp"
37             android:layout_height="wrap_content"
38             android:layout_weight="1"
39             android:gravity="center_horizontal"
40             android:text="密码" />
41 
42         <EditText
43             android:id="@+id/et2"
44             android:layout_width="0dp"
45             android:layout_height="wrap_content"
46             android:layout_marginRight="5dp"
47             android:layout_weight="4"
48             android:background="@drawable/app_pref_bg"
49             android:inputType="textPassword" />
50     </LinearLayout>
51     <LinearLayout 
52         android:layout_width="match_parent"
53         android:layout_height="wrap_content"
54         android:layout_marginTop="10dp"
55         android:orientation="horizontal">
56         <Button 
57             android:id="@+id/btn1"
58             android:layout_width="70dp"
59             android:layout_height="45dp"
60             android:layout_marginLeft="90dp"
61             android:text="登录"
62             android:gravity="center"
63             />
64          <Button 
65             android:id="@+id/btn2"
66             android:layout_width="70dp"
67             android:layout_height="45dp"
68             android:layout_marginLeft="20dp"
69             android:text="注册"
70             android:gravity="center"
71             />
72         
73     </LinearLayout>
74 
75 </LinearLayout>

注册布局xml：

<?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" >

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        android:paddingTop="50dp" >

        <TextView
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:gravity="center_horizontal"
            android:text="账号" />

        <EditText
            android:id="@+id/et1"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginRight="5dp"
            android:layout_weight="4"
            android:background="@drawable/app_pref_bg" />
    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="10dp"
        android:orientation="horizontal" >

        <TextView
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:gravity="center_horizontal"
            android:text="密码" />

        <EditText
            android:id="@+id/et2"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginRight="5dp"
            android:layout_weight="4"
            android:background="@drawable/app_pref_bg"
            android:inputType="textPassword" />
    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="10dp"
        android:orientation="horizontal" >

        <Button
            android:id="@+id/btn1"
            android:layout_width="70dp"
            android:layout_height="45dp"
            android:layout_marginLeft="110dp"
            android:gravity="center"
            android:text="注册" />
    </LinearLayout>

</LinearLayout>

登录成功布局xml：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/ll"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#CEDDED"
    android:orientation="vertical" >
    <TextView 
        android:id="@+id/tv"
        android:layout_width="match_parent"
        android:layout_height="100dp"
        android:background="#1285F0"
        android:textSize="20sp"
        android:gravity="center"
        />
    <Button 
        android:id="@+id/btn"
        android:layout_width="150dp"
        android:layout_height="50dp"
        android:text="点击获取图片"
        android:background="@drawable/btn1"
        android:textSize="20sp"
        android:gravity="center"
        android:layout_gravity="center_horizontal"
        android:layout_marginTop="10dp"
        
        />
    <ImageView 
        android:id="@+id/iv"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:layout_marginTop="10dp"
        
        />
</LinearLayout>

登录主页面JAVA代码：

 1 package com.qf.login;
 2 
 3 import android.app.Activity;
 4 import android.content.Context;
 5 import android.content.Intent;
 6 import android.content.SharedPreferences;
 7 import android.os.Bundle;
 8 import android.text.TextUtils;
 9 import android.view.View;
10 import android.view.View.OnClickListener;
11 import android.widget.Button;
12 import android.widget.EditText;
13 import android.widget.Toast;
14 
15 public class MainActivity extends Activity implements OnClickListener {
16     private EditText et1;
17     private EditText et2;
18     
19     @Override
20     protected void onCreate(Bundle savedInstanceState) {
21         super.onCreate(savedInstanceState);
22         setContentView(R.layout.activity_main);
23 
24           et1 = (EditText) findViewById(R.id.et1);
25           et2 = (EditText) findViewById(R.id.et2);
26         Button btn1 = (Button) findViewById(R.id.btn1);
27         Button btn2 = (Button) findViewById(R.id.btn2);
28 
29         btn1.setOnClickListener(this);
30         btn2.setOnClickListener(this);
31     }
32 
33     public void login() {
34         //获得输入的账户信息
35         String username = et1.getText().toString().trim();
36         String password = et2.getText().toString().trim();
37         //获得SharPreferences中存储的账户信息
38         SharedPreferences sp=getSharedPreferences("userinfo", Context.MODE_PRIVATE);
39 
40         // d.判断用户名密码
41         if (TextUtils.isEmpty(username) || TextUtils.isEmpty(password)) {
42             Toast.makeText(MainActivity.this, "用户名密码不能为空", Toast.LENGTH_SHORT)
43                     .show();
44             return;
45         }else if(username.equals(sp.getString("user", ""))&&password.equals(sp.getString("password", ""))){
46             //跳转到登录成功页面
47             Intent intent=new Intent(MainActivity.this,SuccessLogin.class);
48             
49             startActivity(intent);
50         }else if(!username.equals(sp.getString("user", ""))){
51             Toast.makeText(MainActivity.this, "用户名不存在！请注册", Toast.LENGTH_SHORT).show();
52         }
53         else{
54             Toast.makeText(MainActivity.this, "密码错误", Toast.LENGTH_SHORT).show();
55         }
56     }
57 
58     @Override
59     public void onClick(View v) {
60         switch (v.getId()) {
61         case R.id.btn1:
62             login();
63             break;
64         case R.id.btn2:
65             Intent intent = new Intent(MainActivity.this, Register.class);
66             startActivity(intent);
67             break;
68         default:
69             break;
70         }
71 
72     }
73 
74     
75 
76 }

注册页面JAVA代码：

 1 package com.qf.login;
 2 
 3 import android.app.Activity;
 4 import android.content.Context;
 5 import android.content.Intent;
 6 import android.content.SharedPreferences;
 7 import android.content.SharedPreferences.Editor;
 8 import android.os.Bundle;
 9 import android.view.View;
10 import android.view.View.OnClickListener;
11 import android.widget.Button;
12 import android.widget.EditText;
13 import android.widget.Toast;
14 
15 public class Register extends Activity{
16     @Override
17     protected void onCreate(Bundle savedInstanceState) {
18         // TODO Auto-generated method stub
19         super.onCreate(savedInstanceState);
20         setContentView(R.layout.register);
21         
22         final EditText et1=(EditText) findViewById(R.id.et1);
23         final EditText et2=(EditText) findViewById(R.id.et2);
24         Button btn=(Button) findViewById(R.id.btn1);
25         
26         btn.setOnClickListener(new OnClickListener() {
27             
28             @Override
29             public void onClick(View v) {
30                 //获得主页面传过来的intent
31                 Intent intent=getIntent();
32                 //获得输入的账户信息
33                 String username=et1.getText().toString().trim();
34                 String password=et2.getText().toString().trim();
35                 //SharPreferences存储账户信息
36                 SharedPreferences sp=getSharedPreferences("userinfo", Context.MODE_PRIVATE);
37                 Editor editor=sp.edit();
38                 editor.putString("user", username);
39                 editor.putString("password", password);
40                 editor.commit();
41                 
42                 Toast.makeText(Register.this, "注册成功", Toast.LENGTH_SHORT).show();
43                 //跳回到登录页面
44                 finish();
45             }
46         });
47     }
48 }

登录成功页面JAVA代码：

package com.qf.login;

import java.io.File;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;

import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.graphics.Bitmap;
import android.graphics.Bitmap.CompressFormat;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;

public class SuccessLogin extends Activity {
    Bitmap bmp;
    ImageView iv;
    String str_url = "http://pic1.cxtuku.com/00/09/47/b36872529f7c.jpg";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.success);
        // 获得intent对象
        Intent intent = getIntent();
        //获得存储在SharPreferences的账户信息
        SharedPreferences sp = getSharedPreferences("userinfo",
                Context.MODE_PRIVATE);

        iv = (ImageView) findViewById(R.id.iv);
        
        TextView tv = (TextView) findViewById(R.id.tv);
        tv.setText("欢迎" + sp.getString("user", "") + "登录" + "\n" + "您的密码是："
                + sp.getString("password", ""));
        
        Button btn = (Button) findViewById(R.id.btn);
        //监听点击事件，联网请求异步加载图片
        btn.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                //开启异步线程
                MyBitmapTask task = new MyBitmapTask();
                task.execute(str_url);
                task.setMyInterface(new MyInterface() {

                    @Override
                    public void getImageBitmap(Bitmap bmp) {
                        // TODO Auto-generated method stub

                        //写入到外部存储（SD卡）
                        writeToOutStoragePublic(bmp);
                        //从SD卡中读出图片并显示在屏幕
                        readFromOutStoragePublic();
                    }
                });
                
            }
        });

    }
    
    private void writeToOutStoragePublic(Bitmap bmp) {

        if (Environment.getExternalStorageState().equals(
                Environment.MEDIA_MOUNTED)) {

            File filepath = Environment
                    .getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES);
            File file = new File(filepath, "dahai.jpg");
            try {
                FileOutputStream fos = new FileOutputStream(file);
                bmp.compress(CompressFormat.JPEG, 60, fos);
            } catch (Exception e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
    }

    private void readFromOutStoragePublic() {
        if (Environment.getExternalStorageState().equals(
                Environment.MEDIA_MOUNTED)) {
            File filepath = Environment
                    .getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES);
            File file = new File(filepath, "dahai.jpg");
            try {
                FileInputStream fis = new FileInputStream(file);
                bmp = BitmapFactory.decodeStream(fis);
                iv.setImageBitmap(bmp);
            } catch (Exception e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

        }
    }

}

自定义联网请求工具类代码：

 1 package com.qf.login;
 2 
 3 import java.io.InputStream;
 4 import java.net.HttpURLConnection;
 5 import java.net.URL;
 6 
 7 import android.graphics.Bitmap;
 8 import android.graphics.BitmapFactory;
 9 
10 public class HttpUtils {
11 
12     public static Bitmap downloadImage(String str_url) {
13         Bitmap bmp = null;
14         try {
15             URL url = new URL(str_url);
16             HttpURLConnection conn = (HttpURLConnection) url.openConnection();
17             InputStream is = conn.getInputStream();
18             bmp = BitmapFactory.decodeStream(is);
19         } catch (Exception e) {
20             // TODO Auto-generated catch block
21             e.printStackTrace();
22         }
23         return bmp;
24     };
25 
26 }

自定义接口传值：

1 package com.qf.login;
2 
3 import android.graphics.Bitmap;
4 
5 public interface MyInterface {
6     void getImageBitmap(Bitmap bmp);
7         
8     
9 }

自定义Task类加载图片：

 1 package com.qf.login;
 2 
 3 import android.graphics.Bitmap;
 4 import android.os.AsyncTask;
 5 
 6 public class MyBitmapTask extends AsyncTask<String, Void, Bitmap> {
 7     MyInterface myInterface;
 8     
 9     
10     public void setMyInterface(MyInterface myInterface) {
11         this.myInterface = myInterface;
12     }
13     @Override
14     protected Bitmap doInBackground(String... params) {
15         //加载图片
16         Bitmap bmp=HttpUtils.downloadImage(params[0]);
17         return bmp;
18     }
19     @Override
20     protected void onPostExecute(Bitmap result) {
21         // TODO Auto-generated method stub
22         super.onPostExecute(result);
23         //调用接口实现的方法
24         myInterface.getImageBitmap(result);
25     }
26 }