android 写入文件到ＳＤ卡中去

前面写了一篇Android对文件的基本读写操作，只是向手机自身的存储空间写入文件，但是手机自身的存储空间有限，这时就要考虑向SDCard中存入文件，比如视频，音频和大量的图片。在底层代码的实现上两者没有什么区别，不过想要往SDCard中写入和读取文件首选必须在AndroidManifest.xml 注册权限：

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<!-- 加入在SDCard中创建与删除文件的权限 --> <uses -permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS" /> <!-- 加入在SDCard中写入数据的权限 --> <uses -permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

FileActivity.java 程序主要实现类

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package net.androidla.file;   import java.io.File; import java.io.FileInputStream; import java.io.FileOutputStream;   import net.androidla.service.FileService; import android.app.Activity; 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.EditText; import android.widget.TextView; import android.widget.Toast;   public class FileActivity extends Activity {     private EditText filenameTxt;     private EditText fileContentTxt;     private TextView result;     private Button btnSave;     private Button btnShow;     @Override     public void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.main);         filenameTxt = (EditText) findViewById(R.id.filenameTxt);         fileContentTxt = (EditText) findViewById(R.id.fileContentTxt);         btnSave = (Button) findViewById(R.id.btnSave);         btnShow = (Button) findViewById(R.id.btnShow);         result = (TextView) findViewById(R.id.result);           btnSave.setOnClickListener(listener);         btnShow.setOnClickListener(listener);     }     private View.OnClickListener listener = new OnClickListener() {         @Override         public void onClick(View v) {             Button button = (Button) v;             String filename = filenameTxt.getText().toString();             File file = new File(Environment.getExternalStorageDirectory(), filename);             Log.i("log", file.getAbsolutePath());             switch (button.getId()) {             case R.id.btnSave:                 if (filename != null && !filename.equals("")) {                     try {                         if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {                             FileService.save(new FileOutputStream(file), fileContentTxt.getText().toString());                             Toast.makeText(FileActivity.this, R.string.success, Toast.LENGTH_SHORT).show();                         } else {                             Toast.makeText(FileActivity.this, "sdcard不存在或有写保护", Toast.LENGTH_SHORT).show();                         }                     } catch (Exception e) {                         e.printStackTrace();                     }                 } else {                     Toast.makeText(FileActivity.this, R.string.fail, Toast.LENGTH_SHORT).show();                 }                 break;             case R.id.btnShow:                 try {                     String resultTxt = FileService.read(new FileInputStream(file));                     result.setText(resultTxt);                 } catch (Exception e) {                     Toast.makeText(FileActivity.this, "读取失败", Toast.LENGTH_SHORT).show();                     e.printStackTrace();                 }                 break;             }         }     }; }