Android学习笔记(四)

数据访问

DataActivity

Java代码

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package org.wp.file;   import java.io.File; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.InputStream; import org.wp.service.FileService; import android.app.Activity; import android.os.Bundle; import android.os.Environment; import android.util.Log; import android.view.View; import android.widget.Button; import android.widget.EditText; import android.widget.TextView; import android.widget.Toast;   /** * * Activity还提供了getCacheDir()和getFilesDir()方法: * getCacheDir()方法用于获取/data/data//cache目录 * getFilesDir()方法用于获取/data/data//files目录 * * * * * * * DOS下创建SDCard * 进入Android SDK安装路径的tools目录 * 文件后缀可以随便取 * 建议使用.img * mksdcard 2048M D:\AndroidTool\sdcard.img * * @author wp * */   public class DataActivity extends Activity { private static final String TAG = "DataActivity"; private EditText filenameText; private EditText contentText; private TextView resultView; private Button saveButton; private Button readButton;   @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); filenameText = (EditText) this.findViewById(R.id.filename); contentText = (EditText) this.findViewById(R.id.content); resultView = (TextView) this.findViewById(R.id.result); saveButton = (Button) this.findViewById(R.id.save); readButton = (Button) this.findViewById(R.id.read); saveButton.setOnClickListener(listener); readButton.setOnClickListener(listener); }   private View.OnClickListener listener = new View.OnClickListener() { @Override public void onClick(View arg0) { Button button = (Button) arg0; String filename = filenameText.getText().toString(); File file = new File(Environment.getExternalStorageDirectory(), filename); // File file = new File("/sdcard" + filename); // Environment.getExternalStorageDirectory();   switch (button.getId()) { case R.id.save: // SDCard存在，并且可以进行读写 if (Environment.getExternalStorageState().equals( Environment.MEDIA_MOUNTED)) { int resId = R.string.success; String content = contentText.getText().toString(); try { FileOutputStream outStream = new FileOutputStream(file); FileService.save(outStream, content); } catch (Exception e) { Log.e(TAG, e.toString()); resId = R.string.error; } Toast.makeText(DataActivity.this, resId, Toast.LENGTH_LONG) .show(); } else { Toast.makeText(DataActivity.this, "SDCard不存在或者写保护", Toast.LENGTH_LONG).show(); } break; case R.id.read: try { InputStream inStream = new FileInputStream(file); String text = FileService.read(inStream); resultView.setText(text); } catch (Exception e) { Log.e(TAG, e.toString()); Toast.makeText(DataActivity.this, "读取失败", Toast.LENGTH_LONG).show(); } break; } } }; }

FileService

Java代码

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package org.wp.service;   import java.io.ByteArrayOutputStream; import java.io.InputStream; import java.io.OutputStream;   public class FileService {   /** * 保存数据 * * @param outStream * @param content * @throws Exception */ public static void save(OutputStream outStream, String content) throws Exception { outStream.write(content.getBytes()); outStream.close(); }   /** * 读取数据 * * @param inStream * @return * @throws Exception */ public static String read(InputStream inStream) throws Exception { ByteArrayOutputStream outStream = new ByteArrayOutputStream(); byte[] buffer = new byte[1024]; int len = -1; while ((len = inStream.read(buffer)) != -1) { outStream.write(buffer, 0, len); } byte[] data = outStream.toByteArray(); outStream.close(); inStream.close(); return new String(data); } }

main.xml

Java代码

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version="1.0" encoding="utf-8"?> xmlns:android="" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" > xmlns:android="" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="wrap_content" > android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/filename" android:id="@+id/filenameLable" /> android:layout_width="200px" android:layout_height="wrap_content" android:layout_alignTop="@id/filenameLable" android:layout_toRightOf="@id/filenameLable" android:layout_marginLeft="10px" android:text="wp.txt" android:id="@+id/filename" /> > android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="@string/content" /> android:layout_width="fill_parent" android:layout_height="wrap_content" android:minLines="3" android:id="@+id/content" /> xmlns:android="" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="wrap_content" > android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/save" android:id="@+id/save" /> android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/read" android:layout_toRightOf="@id/save" android:layout_alignTop="@id/save" android:id="@+id/read" /> > android:layout_width="fill_parent" android:layout_height="wrap_content" android:id="@+id/result" /> >

strings.xml

Xml代码

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version="1.0" encoding="utf-8"?> > name="hello">Hello World, DataActivity!> name="app_name">数据保存> name="filename">文件名称> name="content">文件内容> name="save">保存> name="read">读取文件内容> name="success">保存成功> name="error">保存失败> >

AndroidManifest.xml

Xml代码

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version="1.0" encoding="utf-8"?> xmlns:android="" package="org.wp.file" android:versionCode="1" android:versionName="1.0"> android:icon="@drawable/icon" android:label="@string/app_name"> android:name="android.test.runner" /> android:name=".DataActivity" android:label="@string/app_name"> > android:name="android.intent.action.MAIN" /> android:name="android.intent.category.LAUNCHER" /> > > > android:minSdkVersion="7" /> android:name="android.test.InstrumentationTestRunner" android:targetPackage="org.wp.file" android:label="Tests for My App" /> android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS" /> android:name="android.permission.WRITE_EXTERNAL_STORAGE" /> >