Android第五个功能：文件存储到SDCard上面

核心代码四部分：

1、Layout

2、String值

3、MainActivity

4、给项目添加使用授权

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="@string/filename" 
        />
    
    <EditText 
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:id="@+id/filename"
        />
    
        <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="@string/filecontent" 
        />
    
    <EditText 
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:minLines="3"
        android:id="@+id/filecontent"
        />
    
    <Button 
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/button"
        android:id="@+id/button"
        />

</LinearLayout>

package com.dcj.service;

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

import android.content.Context;
import android.os.Environment;

public class FileService {
  private Context context;
  public FileService(Context applicationContext) {
    context = applicationContext;
  }
  
  public void saveToSDCard(String filename, String content) throws Exception {
    File file = new File(Environment.getExternalStorageDirectory(), filename);
    FileOutputStream outStream = new FileOutputStream(file);
    outStream.write(content.getBytes());
    outStream.close();
    
  }
  
  /**
   * 保存文件
   * @param filename 文件名称
   * @param content 文件内容
   * @throws Exception 
   */
  public void save(String filename, String content) throws Exception {
    // IO j2se
    //私有操作模式：创建出来的文件只能被本应用访问，其它应用无法访问该文件，另外采用私有操作创建的文件，写入文件会覆盖原文件内容
    FileOutputStream outStream = context.openFileOutput(filename, context.MODE_PRIVATE);
    outStream.write(content.getBytes());
    outStream.close();
  }
  
  /**
   * 读取文件内容
   * @param filename 文件名称
   * @return 文件内容
   * @throws Exception
   */
  public String read(String filename) throws Exception  {
    FileInputStream inStream = context.openFileInput(filename);
    ByteArrayOutputStream outStream = new ByteArrayOutputStream();
    byte[] buffer = new byte[1024];
    int len = 0;
    while ((len = inStream.read(buffer)) != -1) {
      outStream.write(buffer, 0, len);
    }
    byte[] data = outStream.toByteArray();
    return new String(data);
  }

}

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.dcj"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk android:minSdkVersion="8" />

    <application
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name" >
         <uses-library android:name="android.test.runner" />
        <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>

     <instrumentation
        android:name="android.test.InstrumentationTestRunner"
        android:targetPackage="com.dcj" 
        android:label="Test for my App"/>
     
     <!-- 在SDCard中创建与删除文件权限 -->
 <uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/> 
<!-- 往SDCard写入数据权限 -->
 <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
</manifest>

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

    <string name="hello">Hello World, MainActivity!</string>
    <string name="app_name">存储到程序内部</string>
    <string name="filename">文件名称</string>
    <string name="filecontent">文件内容</string>
    <string name="button">保存</string>
    <string name="success">保存完成</string>
    <string name="fail">保存失败</string>
    <string name="sdcarderror">SDCard不存在或者写保护</string>  
</resources>

package com.dcj;

import com.dcj.service.FileService;

import android.app.Activity;
import android.os.Bundle;
import android.os.Environment;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
import android.widget.SimpleAdapter.ViewBinder;

public class MainActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        Button button = (Button)this.findViewById(R.id.button);
        button.setOnClickListener(new ButtonClickListener());
    }
    
    private final class ButtonClickListener implements View.OnClickListener {
        
        public void onClick(View v) {
            EditText filenameText = (EditText) findViewById(R.id.filename);
            EditText contentText = (EditText) findViewById(R.id.filecontent);
            String filename = filenameText.getText().toString();
            String content = contentText.getText().toString();
            
            FileService service = new FileService(getApplicationContext());
            try {
                //service.save(filename, content);
                //换成保存到SDCard上面
                //判断SDCard是否存在，并且可以读写
                if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {
                    service.saveToSDCard(filename, content);
                    Toast.makeText(getApplicationContext(), R.string.success, 1).show();
                }else{
                    Toast.makeText(getApplicationContext(), R.string.sdcarderror, 1).show();
                }
            } catch (Exception e) {
                Toast.makeText(getApplicationContext(), R.string.fail, 1).show();
                e.printStackTrace();
            }
        }
    }
}