来源: 互联网  发布时间: 2014-02-18

RelativeLayout的一些重要属性
    第一类:属性值为true或false
android:layout_centerhrizontal                                           水平居中
android:layout_centervertical                                            垂直居中
android:layout_centerinparent                                           相对于父元素完全居中
android:layout_alignparentbottom                                     贴紧父元素的下边缘
android:layout_alignparentleft                                          贴紧父元素的左边缘
android:layout_alignparentright                                        贴紧父元素的右边缘
android:layout_alignparenttop                                          贴紧父元素的上边缘
android:layout_alignwithparentifmissing                            如果对应的兄弟元素找不到的话就以父元素做参照物

第二类：属性值必须为id的引用名“@id/id-name”
android:layout_below                          在某元素的下方
android:layout_above                          在某元素的的上方
android:layout_toleftof                       在某元素的左边
android:layout_torightof                     在某元素的右边

android:layout_aligntop                      本元素的上边缘和某元素的的上边缘对齐
android:layout_alignleft                      本元素的左边缘和某元素的的左边缘对齐
android:layout_alignbottom                 本元素的下边缘和某元素的的下边缘对齐
android:layout_alignright                    本元素的右边缘和某元素的的右边缘对齐

第三类：属性值为具体的像素值，如30dip，40px
android:layout_marginbottom              离某元素底边缘的距离
android:layout_marginleft                   离某元素左边缘的距离
android:layout_marginright                 离某元素右边缘的距离
android:layout_margintop                   离某元素上边缘的距离 

    

    来源: 互联网  发布时间: 2014-02-18

将 Object 保存到 SharedPreferences 中

1. MainActivity.java

package powerise.demo01;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.OptionalDataException;
import java.io.StreamCorruptedException;
import java.util.Date;

import org.apache.commons.codec.binary.Base64;

import android.app.Activity;
import android.content.Context;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends Activity {

	private EditText et_id = null;
	private EditText et_name = null;
	private Button btn_save = null;
	private TextView tv_result = null;
	
	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		initGUIElements();
		getObjectInfo();
		
		btn_save.setOnClickListener(new OnClickListener() {
			@Override
			public void onClick(View v) {
				String id = et_id.getText().toString();
				String name = et_name.getText().toString();
				saveObject(id, name);
				getObjectInfo();
			}
		});
	}

	protected void getObjectInfo() {
		try {
			SharedPreferences mSharedPreferences = getSharedPreferences("base64", Context.MODE_PRIVATE);
			String personBase64 = mSharedPreferences.getString("person", "");
			byte[] base64Bytes = Base64.decodeBase64(personBase64.getBytes());
			ByteArrayInputStream bais = new ByteArrayInputStream(base64Bytes);
			ObjectInputStream ois = new ObjectInputStream(bais);
			Person person = (Person) ois.readObject();
			tv_result.setText(person.toString());
		} catch (Exception e) {
			e.printStackTrace();
		}
		
	}

	private void initGUIElements() {
		et_id = (EditText) findViewById(R.id.et_id);
		et_name = (EditText) findViewById(R.id.et_name);
		btn_save = (Button) findViewById(R.id.btn_save);
		tv_result = (TextView) findViewById(R.id.tv_result);
	}

	private void saveObject(String id, String name) {
		SharedPreferences mSharedPreferences = getSharedPreferences("base64", Context.MODE_PRIVATE);
		Person person = new Person(Integer.parseInt(id), name, new Date());
		try {
			ByteArrayOutputStream baos = new ByteArrayOutputStream();
			ObjectOutputStream oos = new ObjectOutputStream(baos);
			oos.writeObject(person);

			String personBase64 = new String(Base64.encodeBase64(baos.toByteArray()));
			SharedPreferences.Editor editor = mSharedPreferences.edit();
			editor.putString("person", personBase64);
			editor.commit();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
}

 

 

2. Person.java

package powerise.demo01;

import java.io.Serializable;
import java.util.Date;

public class Person implements Serializable {
	
	private static final long serialVersionUID = 4318838659250781721L;
	
	private int id;
	private String name;
	private Date birthday;

	public Person(int id, String name, Date birthday) {
		this.id = id;
		this.name = name;
		this.birthday = birthday;
	}

	public int getId() {
		return id;
	}

	public void setId(int id) {
		this.id = id;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public Date getBirthday() {
		return birthday;
	}

	public void setBirthday(Date birthday) {
		this.birthday = birthday;
	}

	@Override
	public String toString() {
		return "Person [id=" + id + ", name=" + name + ", birthday=" + birthday + "]";
	}

}

 

 

3. main.xml

<?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="编号:" />
	<EditText 
		android:id="@+id/et_id"
		android:layout_width="fill_parent"
		android:layout_height="wrap_content"/>
		
	<TextView  
	    android:layout_width="fill_parent" 
	    android:layout_height="wrap_content" 
	    android:text="姓名:" />
	<EditText 
		android:id="@+id/et_name"
		android:layout_width="fill_parent"
		android:layout_height="wrap_content"/>   
	    
	<Button
		android:id="@+id/btn_save"
	    android:layout_width="fill_parent" 
	    android:layout_height="wrap_content" 
	    android:text="保存" />
	    
	<TextView
	    android:layout_width="fill_parent" 
	    android:layout_height="wrap_content" 
	    android:text="结果:" />
	<TextView  
		android:id="@+id/tv_result"
	    android:layout_width="fill_parent" 
	    android:layout_height="wrap_content"/>
</LinearLayout>

 

 

小记:

        保存 Object 对象, 最终是以 String 形式保存在 SharedPreferences 中.

        首先将 Object 对象放入到 Object输出流中(ObjectOutputStream), 再用 Base64 将流转换 byte[]

 

        读取 Object 对象, 则相反

 

注意: 要在 http://commons.apache.org/codec/download_codec.cgi 中下载 Base64 jar 包并添加到 BuildPath 中.

    

    来源: 互联网  发布时间: 2014-02-18

常用到的Intent的URI