Android开发学习---android下的数据持久化,保存数据到rom文件,android_data目录下文件访问的权限控制

时间：2014-05-22 14:28:57 阅读：775 评论：0 收藏：0 [点我收藏+]

标签：android style blog class c code

一.需求

做一个类似QQ登录似的app,将数据写到ROM文件里,并对数据进行回显.

二.截图

登录界面:

bubuko.com,布布扣

文件浏览器,查看文件的保存路径:/data/data/com.amos.datasave/files/LoginTest.txt------/data/data/(包名)/files/(文件名)

bubuko.com,布布扣

导出的文件内容:

bubuko.com,布布扣

三.实现代码

新建一个Android 工程.这里我选择的是2.1即API 7,进行开发的,其它都是默认下一步下一步即可.

/datasave/res/layout/activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_info" />

    <EditText
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:numeric="integer" 
        android:inputType="text|number"
        android:hint="@string/et_type_name"
        android:id="@+id/et_name"
        />
    <EditText 
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:inputType="textPassword"
        android:hint="@string/et_type_password"
        android:id="@+id/et_password"
        />

    <RelativeLayout
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
     >
        <Button
            android:id="@+id/bt_login"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentLeft="true"
            android:layout_alignParentTop="true"
            android:layout_marginLeft="30dp"
            android:text="@string/bt_login" />
        
        <CheckBox 
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginLeft="150dp"
            android:text="@string/cb_remember_password"     
            android:id="@+id/cb_password"                   
            />
        
        
    </RelativeLayout>

</LinearLayout>

这里需要介绍的是android:hint属性,作用是输入框里的显示的提示信息.相当于web项目中的placeholder.

/datasave/res/values/strings.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>

    <string name="app_name">手机qq登录save</string>
    <string name="action_settings">Settings</string>
    <string name="hello_info">请输入账号和密码:</string>
    <string name="et_type_name">请输入账号</string>
    <string name="et_type_password">请输入密码</string>
    <string name="bt_login">登   录</string>
    <string name="cb_remember_password">记住密码</string>
    
</resources>

/datasave/src/com/amos/datasave/MainActivity.java

package com.amos.datasave;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends Activity implements OnClickListener {

    String tag = "MainActivity";
    EditText et_name;//用户名
    EditText et_password;//密码
    Button bt_login;//登录按钮
    CheckBox cb_password;//单选框

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //初始化
        et_name = (EditText) this.findViewById(R.id.et_name);
        et_password = (EditText) this.findViewById(R.id.et_password);
        bt_login = (Button) this.findViewById(R.id.bt_login);
        cb_password = (CheckBox) this.findViewById(R.id.cb_password);
        
        //注册点击事件
        bt_login.setOnClickListener(this);

    }

    // 点击事件
    @Override
    public void onClick(View v) {
        switch (v.getId()) {
        case R.id.bt_login:

            if (cb_password.isChecked()) {//如果单选框被选中了
                //保存数据到rom
                new savePasswordService(this).savePasswordToFile(et_name.getText().toString(), et_password.getText().toString());
                Toast.makeText(this, "保存数据成功!", Toast.LENGTH_SHORT).show();
            } else {
                Toast.makeText(this, "没有保存数据!", Toast.LENGTH_SHORT).show();
            }
        }
    }
}

注:这里主要注意的是进行判断时使用switch语句能更使代码结构更清晰.

/datasave/src/com/amos/datasave/savePasswordService.java

package com.amos.datasave;

import java.io.FileOutputStream;

import android.annotation.SuppressLint;
import android.content.Context;
import android.util.Log;

@SuppressLint("WorldWriteableFiles")
public class savePasswordService {
    private Context context;

    private String tag = "savePasswordService";

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

    public void savePasswordToFile(String name, String password) {
        // 这里设置文件的权限
        String content = name + ":" + password;
        Log.d(tag, "设置文件的读写权限");
        try {
            FileOutputStream fileOutput = context.openFileOutput("LoginTestConfig.txt", Context.MODE_WORLD_READABLE | Context.MODE_WORLD_WRITEABLE);
            fileOutput.write(content.getBytes());
            fileOutput.flush();
            fileOutput.close();
        } catch (Exception e) {
            Log.d(tag, "设置文件的读写权限失败!");
            e.printStackTrace();
        }

    }

}

注:这里是将用户名密码写到rom中的关键所在,主要调用了Context中的openFileOutput()方法,默认的权限是private,即其他应用程序不可读,这里我设置了其它应用程序可读写.

这里新建一个工程叫dataread,其界面设计不变,这里读取到LoginTestConfig.txt,然后往里面写数据,实验证明是OK的,写入成功.

package com.amos.dataread;

import java.io.File;
import java.io.FileOutputStream;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.EditText;

public class MainActivity extends Activity {
    private String tag = "MainActivity";
    EditText et_name;
    EditText et_password;
    Button bt_login;
    CheckBox cb_remember;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Log.d(tag, "准备读取数据");
        File file = new File("/data/data/com.amos.datasave/files/LoginTestConfig.txt");
        try {
            FileOutputStream fos =new FileOutputStream(file);
            fos.write("112233:pwd".getBytes());
            fos.close();
            
        } catch (Exception e) {
            e.printStackTrace();
        }

    }

}

如果想要实现数据回显,那么可以参考以下代码:

package com.amos.dataread;

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

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends Activity {
    private String tag = "MainActivity";
    EditText et_name;
    EditText et_password;
    Button bt_login;
    CheckBox cb_remember;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        et_name = (EditText) this.findViewById(R.id.et_name);
        et_password = (EditText) this.findViewById(R.id.et_password);
        
        Log.d(tag, "准备读取数据");
        File file = new File("/data/data/com.amos.datasave/files/LoginTestConfig.txt");
        try {
            FileInputStream fis= new FileInputStream(file);
            byte[] bytes = new byte[1024];
            
            ByteArrayOutputStream bos = new ByteArrayOutputStream();
            int len;
            while((len=fis.read(bytes))>0){
                bos.write(bytes, 0, len);
            }
            String result = new String(bos.toByteArray());
            Log.d(tag, result);
            Toast.makeText(this, "读取数据成功!"+result, Toast.LENGTH_LONG);
            String name = result.split(":")[0];
            String password = result.split(":")[1];
            Log.d(tag,name);
            Log.d(tag,password);
            et_name.setText(name);
            et_password.setText(password);
        } catch (Exception e) {
            e.printStackTrace();
        }

    }

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

}

效果:

这个是写数据.

bubuko.com,布布扣

这个是读数据,即将数据回显.

bubuko.com,布布扣

这里一定要注意初始化EditText 输入框,否则会一直报空指针的错误.如下所示:

05-21 16:36:23.127: D/MainActivity(31834): 123456:password
05-21 16:36:23.173: W/System.err(31834): java.lang.NullPointerException
05-21 16:36:23.183: W/System.err(31834):     at com.amos.dataread.MainActivity.onCreate(MainActivity.java:43)
05-21 16:36:23.193: W/System.err(31834):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
05-21 16:36:23.193: W/System.err(31834):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2459)
05-21 16:36:23.193: W/System.err(31834):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2512)
05-21 16:36:23.193: W/System.err(31834):     at android.app.ActivityThread.access$2200(ActivityThread.java:119)
05-21 16:36:23.193: W/System.err(31834):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1863)
05-21 16:36:23.193: W/System.err(31834):     at android.os.Handler.dispatchMessage(Handler.java:99)
05-21 16:36:23.203: W/System.err(31834):     at android.os.Looper.loop(Looper.java:123)
05-21 16:36:23.203: W/System.err(31834):     at android.app.ActivityThread.main(ActivityThread.java:4363)
05-21 16:36:23.213: W/System.err(31834):     at java.lang.reflect.Method.invokeNative(Native Method)
05-21 16:36:23.213: W/System.err(31834):     at java.lang.reflect.Method.invoke(Method.java:521)
05-21 16:36:23.213: W/System.err(31834):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860)
05-21 16:36:23.223: W/System.err(31834):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
05-21 16:36:23.223: W/System.err(31834):     at dalvik.system.NativeStart.main(Native Method)