Android 学习笔记7---数据存储与访问

1. 文件
2. SharedPreferences
3. SQLite数据库
4. 内容提供者（Content provider）(对外共享数据使用)
5. 网络

本文讲讲文件的例子，其余后续讲解。

例子采用MVC模式

1业务bean（junit test） 2设计界面（美工） 这两项工作可以同步进行

3设计activity

android 内部类 为了性能，尽量少用类，合理。

例子

运行后截图

目录结构：

代码:

package com.leo.file;

import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

import com.leo.service.FileService;

public class DataActivity extends Activity {
	private static final String TAG = "DataActivity";
    private EditText filenameText;
    private EditText contentText;
    private TextView resultView;
    
    @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);
        Button button = (Button)this.findViewById(R.id.button);
        Button showButton = (Button)this.findViewById(R.id.showButton);
        
        button.setOnClickListener(listner);
        showButton.setOnClickListener(listner);
    }
    
    private View.OnClickListener listner = new View.OnClickListener() {		
		
		public void onClick(View v) {
			Button button = (Button)v;
			String filename = filenameText.getText().toString();
			
			
			switch (button.getId()){
			case R.id.button:
				int resId = R.string.success;				
				String content = contentText.getText().toString();
				
				try {
					OutputStream outStream = DataActivity.this.openFileOutput(filename, 
							Context.MODE_WORLD_READABLE + Context.MODE_WORLD_WRITEABLE);
					FileService.save(outStream, content);
				} catch (IOException e) {
					Log.e(TAG, e.toString());
					resId = R.string.error;
				}
				Toast.makeText(DataActivity.this, resId, Toast.LENGTH_LONG).show();
				break;
				
			case R.id.showButton:
				try {				
					InputStream inStream = DataActivity.this.openFileInput(filename);
					String text = FileService.read(inStream);
					resultView.setText(text);
				} catch (IOException e) {
					Log.e(TAG, e.toString());	
					Toast.makeText(DataActivity.this, "read error", Toast.LENGTH_LONG).show();
				}
				break;				
			}

		}
	};
}

package com.leo.file;

import java.io.InputStream;
import java.io.OutputStream;

import android.content.Context;
import android.test.AndroidTestCase;
import android.util.Log;

import com.leo.service.FileService;

public class FileServiceTest extends AndroidTestCase {
	private static final String TAG = "FileServiceTest";
	
	public void testSave() throws Exception {
		OutputStream outStream = this.getContext().openFileOutput("leo.txt", Context.MODE_PRIVATE);
		FileService.save(outStream, "leo");
	}
	
	public void testread() throws Exception {
		InputStream inStream = this.getContext().openFileInput("leo.txt");
		String content = FileService.read(inStream);
		Log.i(TAG, content);
	}
}

package com.leo.service;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

public class FileService {
	/**
	 * 保存数据
	 * @param outStream
	 * @param content
	 * @throws IOException
	 */
	public static void save (OutputStream outStream, String content) throws IOException {
		outStream.write(content.getBytes());
		outStream.close();
	}
	/**
	 * 读取数据
	 * @param inStream
	 * @return
	 * @throws IOException
	 */
	public static String read (InputStream inStream) throws IOException {
		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);
		
	}
}

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <string name="hello">Hello World, DataActivity!</string>
    <string name="app_name">数据保存</string>
    <string name="filename">文件名称</string>
    <string name="content">文件内容</string>
    <string name="save">保存</string>
     <string name="show">显示文件内容</string>
    <string name="error">保存失败</string>
    <string name="success">保存成功</string>
</resources>

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

    <application android:icon="@drawable/icon" android:label="@string/app_name">
   		<uses-library android:name="android.test.runner" />
        <activity android:name=".DataActivity"
                  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.leo.file" android:label="Tests for My App" />
</manifest>

附件：https://files.cnblogs.com/khldragon/File.zip