黎活明8天快速掌握android视频教程--14_把文件存放在SDCard

把文件保存在手机的内部存储空间中

1 首先必须在清单文件中添加权限

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="contract.test.savafileapplication" >

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".MyActivity"
            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>
    <!-- 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>

1、我们来看下业务层的代码，业务层的异常不要进行处理交给控制层activity进行处理，activity通过业务层返回的异常就知道业务是否操作成功，就可以在界面上做出相应的显示了

package contract.test.savafileapplication;

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

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

public class FileService {
    private Context context;

    public FileService(Context context) {
        this.context = context;
    }

    public   void saveTosdCard(String fileName, String fileContext) throws Exception {

        File file  = new File(Environment.getExternalStorageDirectory(),fileName);
       FileOutputStream fileOutputStream =  new FileOutputStream(file);
       fileOutputStream.write(fileContext.getBytes());
       fileOutputStream.close();
   }

    public  String readFromSdCard(String filename) throws IOException
    {
        File file  = new File(Environment.getExternalStorageDirectory(),filename);
        FileInputStream fileInputStream = new FileInputStream(file);

        byte[] bytes = new byte[1024];
        ByteArrayOutputStream  byteArrayOutputStream = new ByteArrayOutputStream();
        /*byte是基本数据类型  如int类型
          Byte是byte的包装类*/
        int len = 0;
        while ((len = fileInputStream.read(bytes))!=-1)
        {

           byteArrayOutputStream.write(bytes,0,len);
        }
        byteArrayOutputStream.close();
        fileInputStream.close();
        String str = new String(byteArrayOutputStream.toString());
        return  str;
    }
}

activity的代码：

package contract.test.savafileapplication;

import android.app.Activity;
import android.os.Bundle;
import android.os.Environment;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

import java.io.IOException;

public class MyActivity extends Activity {
    private Button save , show;
    private EditText filename, filecontext;
    private TextView showContext;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_my);
        save = (Button)this.findViewById(R.id.saveButton);
        show = (Button)this.findViewById(R.id.showButton);
        filename = (EditText)this.findViewById(R.id.fileName_ET);
        filecontext = (EditText)this.findViewById(R.id.saveContext_ET);

        showContext = (TextView)this.findViewById(R.id.showConTextView);

        save.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
              String name =  filename.getText().toString();
              String context = filecontext.getText().toString();
              FileService fileService = new FileService(getApplicationContext());
                try {
                    if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED))
                    {
                        fileService.saveTosdCard(name,context);
                        Toast.makeText(getApplicationContext(),"文件保存成功！",Toast.LENGTH_LONG).show();

                    }
                    else
                    {
                        Toast.makeText(getApplicationContext(),"sdCard不存在或者写保护！",Toast.LENGTH_LONG).show();
                    }

                } catch (Exception e) {
                    Toast.makeText(getApplicationContext(),"文件保存失败！",Toast.LENGTH_LONG).show();
                    e.printStackTrace();
                }
            }
        });
        show.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
              FileService fileService = new FileService(getApplicationContext());
                String name =  filename.getText().toString();
                try {
                    if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED))
                    {
                        String str = fileService.readFromSdCard(name);
                        Toast.makeText(getApplicationContext(),"文件读取成功！",Toast.LENGTH_LONG).show();
                        showContext.setText(str);
                    }
                    else
                    {
                        Toast.makeText(getApplicationContext(),"sdCard不存在或者写保护！",Toast.LENGTH_LONG).show();
                    }

                } catch (IOException e) {
                    e.printStackTrace();
                    Toast.makeText(getApplicationContext(),"文件读取失败！",Toast.LENGTH_LONG).show();
                }
            }
        });

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.my, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
}

xml的代码：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="请输入要保存的文件名:"
        />
    <EditText
        android:id="@+id/fileName_ET"
        android:layout_width="fill_parent"
        android:layout_height="50dp"
        android:hint="请输入要保存的文件名！"
        />
    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="请您输入要保存的内容："
        />
    <EditText
        android:id="@+id/saveContext_ET"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:hint="请您在此处输入文件内容！"
        />
    <Button
        android:id="@+id/saveButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="save"
        />
    <Button
        android:id="@+id/showButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="show"
        />
    <TextView
        android:id="@+id/showConTextView"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        />
</LinearLayout>