在Android系统中,这些文件保存在 /data/data/PACKAGE_NAME/files 目录下。
数据读取
public static String read(Context context, String file) {
String data = "";
try {
FileInputStream stream = context.openFileInput(file);
StringBuffer sb = new StringBuffer();
int c;
while ((c = stream.read()) != -1) {
sb.append((char) c);
}
stream.close();
data = sb.toString();
} catch (FileNotFoundException e) {
} catch (IOException e) {
}
return data;
}
从代码上,看起来唯一的不同就是文件的打开方式了: context.openFileInput(file); Android中的文件读写具有权限控制,所以使用context(Activity的父类)来打开文件,文件在相同的Package***享。这里的 Package的概念同Preferences中所述的Package,不同于Java中的Package。
数据写入
public static void write(Context context, String file, String msg) {
try {
FileOutputStream stream = context.openFileOutput(file,
Context.MODE_WORLD_WRITEABLE);
stream.write(msg.getBytes());
stream.flush();
stream.close();
} catch (FileNotFoundException e) {
} catch (IOException e) {
}
}
在这里打开文件的时候,声明了文件打开的方式。
一般来说,直接使用文件可能不太好用,尤其是,我们想要存放一些琐碎的数据,那么要生成一些琐碎的文件,或者在同一文件中定义一下格式。其实也可以将其包装成Properties来使用:
public static Properties load(Context context, String file) {
Properties properties = new Properties();
try {
FileInputStream stream = context.openFileInput(file);
properties.load(stream);
} catch (FileNotFoundException e) {
} catch (IOException e) {
}
return properties;
}
public static void store(Context context, String file, Properties properties) {
try {
FileOutputStream stream = context.openFileOutput(file,
Context.MODE_WORLD_WRITEABLE);
properties.store(stream, "");
} catch (FileNotFoundException e) {
} catch (IOException e) {
}
}
/Chapter09_Data_02/src/com/amaker/test/MainActivity.java
- 代码package com.amaker.test;
-
-
import java.io.FileInputStream;
-
import java.io.FileOutputStream;
-
-
import android.app.Activity;
-
import android.os.Bundle;
-
import android.view.View;
-
import android.view.View.OnClickListener;
-
import android.widget.Button;
-
import android.widget.EditText;
-
-
public class MainActivity extends Activity {
-
private static final String FILE_NAME="temp.txt";
-
private Button b1,b2;
-
private EditText et1,et2;
-
@Override
-
public void onCreate(Bundle savedInstanceState) {
-
super.onCreate(savedInstanceState);
- setContentView(R.layout.main);
- b1 = (Button)findViewById(R.id.Button01);
- b2 = (Button)findViewById(R.id.Button02);
-
- et1 = (EditText)findViewById(R.id.EditText01);
- et2 = (EditText)findViewById(R.id.EditText02);
-
-
b1.setOnClickListener(new OnClickListener() {
-
@Override
-
public void onClick(View v) {
- write(et1.getText().toString());
- }
- });
-
-
b2.setOnClickListener(new OnClickListener() {
-
@Override
-
public void onClick(View v) {
- et2.setText(read());
- }
- });
- }
-
-
private String read(){
-
try {
- FileInputStream fis = openFileInput(FILE_NAME);
-
byte[] buffer = new byte[fis.available()];
- fis.read(buffer);
-
return new String(buffer);
-
} catch (Exception e) {
- e.printStackTrace();
- }
-
return null;
- }
-
-
private void write(String content){
-
try {
- FileOutputStream fos = openFileOutput(FILE_NAME, MODE_APPEND);
- fos.write(content.getBytes());
- fos.close();
-
} catch (Exception e) {
- e.printStackTrace();
- }
- }
- }
-
-
-
- /Chapter09_Data_02/res/layout/main.xml
- 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="File Test" />
-
-
<EditText android:text="" android:id="@+id/EditText01"
-
android:layout_width="fill_parent" android:layout_height="wrap_content" android:height="100px"></EditText>
-
-
<Button android:id="@+id/Button01" android:layout_width="wrap_content"
-
android:layout_height="wrap_content" android:text="Write"></Button>
-
-
<EditText android:text="" android:id="@+id/EditText02"
-
android:layout_width="fill_parent" android:layout_height="wrap_content" android:height="100px"></EditText>
-
-
<Button android:id="@+id/Button02" android:layout_width="wrap_content"
-
android:layout_height="wrap_content" android:text="Read"></Button>
-
- </LinearLayout>
-
-
-
-
- /Chapter09_Data_02/AndroidManifest.xml
- 代码<?xml version="1.0" encoding="utf-8"?>
-
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
-
package="com.amaker.test"
-
android:versionCode="1"
-
android:versionName="1.0">
-
<application android:icon="@drawable/icon" android:label="@string/app_name">
-
<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>
-
<uses-sdk android:minSdkVersion="3" />
-
- </manifest>
本文转自linzheng 51CTO博客,原文链接:http://blog.51cto.com/linzheng/1079365