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
1 <??> 2 <manifest ="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.INTE.NET"/>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 <application18 android:allowBackup="true"19 android:icon="@drawable/ic_launcher"20 android:label="@string/app_name"21 android:theme="@style/AppTheme" >22 <activity23 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 ="http://schemas.android.com/apk/res/android" 2 ="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 <TextView14 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 <EditText21 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 <LinearLayout30 android:layout_width="match_parent"31 android:layout_height="wrap_content"32 android:layout_marginTop="10dp"33 android:orientation="horizontal" >34 35 <TextView36 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 <EditText43 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
<??><LinearLayout ="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
<??><LinearLayout ="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 @Override20 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 @Override59 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 @Override17 protected void onCreate(Bundle savedInstanceState) {18 // TODO Auto-generated method stub19 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 @Override29 public void onClick(View v) {30 //获得主页面传过来的intent31 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 block21 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 @Override14 protected Bitmap doInBackground(String... params) {15 //加载图片16 Bitmap bmp=HttpUtils.downloadImage(params[0]);17 return bmp;18 }19 @Override20 protected void onPostExecute(Bitmap result) {21 // TODO Auto-generated method stub22 super.onPostExecute(result);23 //调用接口实现的方法24 myInterface.getImageBitmap(result);25 }26 }运行结果展示：
images/loading.gif' data-original="http://images2015.cnblogs.com/blog/915324/201608/915324-20160816234443171-44500641.png" />
代码中若有不足欢迎留言建议！谢谢
原标题：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）
关键词：登录
我知道了 