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基于Bmob的Android资讯类app开发（一）

2017-04-17 21:01 375 查看

这个小app仅是为了熟悉Bmob和Android而开发的，一些很基础的东西，记录下来。

一、app介绍：

一个UFO、灵异事件和未解之谜相关兴趣的资讯展示和讨论社区。主页包括头条新闻、灵异事件资讯、未解之谜资讯、社区。前三部分结构完全一样，仅仅为了在ListView上展示Bmob的数据，社区功能可以发贴和评论，也是为了熟悉Bmob的数据操作。此外还包括注册和登录功能。个人中心界面仅作跳转（页面功能未实现）。

二、Bmob简介：

Bmob是什么？Bmob是一个后台管理程序，Bmob 为你提供了实时数据与文件存储功能，轻松实现应用“云与端”的数据连通。数据存储除了常规应用文本信息的存储，还可以存储图片、视频、音频、地理位置等信息。

此外数据服务还内置用户系统、即时通讯、权限控制等，开发者几行代码即可实现快速集成。

上面是官方介绍，简言之，Bmob就是一个云数据库，可以方便的管理数据，将数据加载到Android的app中，简化后台开发，很方便也很简单，适合于做毕业设计的同学们以及快速开发个人app，哈哈。

三、主页面设计

这个页面在第一篇文章中有详细的介绍。这里不再赘述。

Android选项卡TabLayout简单使用

四、导入Bmob sdk

这部分是使用Bmob的基本方法，建议转移到Bmob官网查看文档，文档非常详细。

文档地址：点击进入

五、ListView加载Bmob上的数据

1.list_item_card_main.xml ListView的item布局文件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal" android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@color/white">
<ImageView
android:id="@+id/head_pic"
android:layout_width="100dp"
android:layout_height="120dp"
android:adjustViewBounds="true"
android:src="@drawable/logo"
/>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginLeft="20dp"
android:orientation="vertical">
<TextView
android:id="@+id/head_title"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="10dp"
android:maxLines="2"
android:text="UFO之谜"
android:textColor="@color/black"
android:textSize="20sp"/>
<TextView
android:id="@+id/head_describe"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="10dp"
android:maxLines="3"
android:text="UFO（Unidentified Flying Object ），不明飞行物是指不明来历、不明空间、不明结构、不明性质，但又漂浮、飞行在空中的物体。"
android:textColor="#666"
android:textSize="15sp"/>
</LinearLayout>
</LinearLayout>

2.list_head.xml 头条布局文件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">
<ListView
android:id="@+id/list_head"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:descendantFocusability="blocksDescendants"
/>
</LinearLayout>

3.HeadAdapter.java 头条适配器

package com.example.wjy329.ufo.Adapter;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;
import com.example.wjy329.ufo.Bean.head;
import com.example.wjy329.ufo.R;
import com.example.wjy329.ufo.Tools.ImageLoader;
import java.util.List;
/**
* Created by wjy329 on 2017/3/4.
*/

public class HeadAdapter extends BaseAdapter{
List<head> hl;
LayoutInflater inflater;
public ImageLoader imageLoader;
public HeadAdapter(Context context,List<head> heads){
this.hl = heads;
inflater = LayoutInflater.from(context);
imageLoader = new ImageLoader(context.getApplicationContext());
}

@Override
public int getCount() {
return hl.size();
}

@Override
public Object getItem(int position) {
return hl.get(position);
}

@Override
public long getItemId(int position) {
return position;
}

@Override
public View getView(final int position,View convertView,ViewGroup parent) {
ViewHolder holder;
if(convertView ==null){
holder = new ViewHolder();
convertView = inflater.inflate(R.layout.list_item_card_main,null);
holder.head_picture = (ImageView) convertView.findViewById(R.id.head_pic);
holder.head_title = (TextView) convertView.findViewById(R.id.head_title);
holder.head_describe = (TextView) convertView.findViewById(R.id.head_describe);
convertView.setTag(holder);
}else{
holder = (ViewHolder) convertView.getTag();
}
final head head = hl.get(position);
imageLoader.DisplayImage(head.getPicture(),holder.head_picture);
holder.head_title.setText(head.getTitle());
holder.head_describe.setText(head.getDescribe());
return convertView;
}

static class ViewHolder {
ImageView head_picture;
TextView head_title;
TextView head_describe;
}
}

上面的ImageLoader是一个加载网络图片的方法。
ImageLoader.java

package com.example.wjy329.ufo.Tools;

/**
* Created by wjy32 on 2016/3/2.
*/

import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.widget.ImageView;

import com.example.wjy329.ufo.R;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.Collections;
import java.util.Map;
import java.util.WeakHashMap;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class ImageLoader {

MemoryCache memoryCache=new MemoryCache();
FileCache fileCache;
private Map<ImageView, String> imageViews=Collections.synchronizedMap(new WeakHashMap<ImageView, String>());
ExecutorService executorService;

public ImageLoader(Context context){
fileCache=new FileCache(context);
executorService=Executors.newFixedThreadPool(5);
}

final int stub_id = R.drawable.mao;
public void DisplayImage(String url, ImageView imageView)
{
imageViews.put(imageView, url);
Bitmap bitmap=memoryCache.get(url);
if(bitmap!=null)
imageView.setImageBitmap(bitmap);
else
{
queuePhoto(url, imageView);
imageView.setImageResource(stub_id);
}
}

private void queuePhoto(String url, ImageView imageView)
{
PhotoToLoad p=new PhotoToLoad(url, imageView);
executorService.submit(new PhotosLoader(p));
}

private Bitmap getBitmap(String url)
{
File f=fileCache.getFile(url);

//从sd卡
Bitmap b = decodeFile(f);
if(b!=null)
return b;

//从网络
try {
Bitmap bitmap=null;
URL imageUrl = new URL(url);
HttpURLConnection conn = (HttpURLConnection)imageUrl.openConnection();
conn.setConnectTimeout(30000);
conn.setReadTimeout(30000);
conn.setInstanceFollowRedirects(true);
InputStream is=conn.getInputStream();
OutputStream os = new FileOutputStream(f);
Utils.CopyStream(is, os);
os.close();
bitmap = decodeFile(f);
return bitmap;
} catch (Exception ex){
ex.printStackTrace();
return null;
}
}

//解码图像用来减少内存消耗
private Bitmap decodeFile(File f){
try {
//解码图像大小
BitmapFactory.Options o = new BitmapFactory.Options();
o.inJustDecodeBounds = true;
BitmapFactory.decodeStream(new FileInputStream(f),null,o);

//找到正确的刻度值，它应该是2的幂。
final int REQUIRED_SIZE=70;
int width_tmp=o.outWidth, height_tmp=o.outHeight;
int scale=1;
while(true){
if(width_tmp/2<REQUIRED_SIZE || height_tmp/2<REQUIRED_SIZE)
break;
width_tmp/=2;
height_tmp/=2;
scale*=2;
}

BitmapFactory.Options o2 = new BitmapFactory.Options();
o2.inSampleSize=scale;
return BitmapFactory.decodeStream(new FileInputStream(f), null, o2);
} catch (FileNotFoundException e) {}
return null;
}

//任务队列
private class PhotoToLoad
{
public String url;
public ImageView imageView;
public PhotoToLoad(String u, ImageView i){
url=u;
imageView=i;
}
}

class PhotosLoader implements Runnable {
PhotoToLoad photoToLoad;
PhotosLoader(PhotoToLoad photoToLoad){
this.photoToLoad=photoToLoad;
}

@Override
public void run() {
if(imageViewReused(photoToLoad))
return;
Bitmap bmp=getBitmap(photoToLoad.url);
memoryCache.put(photoToLoad.url, bmp);
if(imageViewReused(photoToLoad))
return;
BitmapDisplayer bd=new BitmapDisplayer(bmp, photoToLoad);
Activity a=(Activity)photoToLoad.imageView.getContext();
a.runOnUiThread(bd);
}
}

boolean imageViewReused(PhotoToLoad photoToLoad){
String tag=imageViews.get(photoToLoad.imageView);
if(tag==null || !tag.equals(photoToLoad.url))
return true;
return false;
}

//用于显示位图在UI线程
class BitmapDisplayer implements Runnable
{
Bitmap bitmap;
PhotoToLoad photoToLoad;
public BitmapDisplayer(Bitmap b, PhotoToLoad p){bitmap=b;photoToLoad=p;}
public void run()
{
if(imageViewReused(photoToLoad))
return;
if(bitmap!=null)
photoToLoad.imageView.setImageBitmap(bitmap);
else
photoToLoad.imageView.setImageResource(stub_id);
}
}

public void clearCache() {
memoryCache.clear();
fileCache.clear();
}

}

FileCache.java

package com.example.wjy329.ufo.Tools;

/**
* Created by wjy32 on 2016/3/2.
*/
import android.content.Context;

import java.io.File;

public class FileCache {

private File cacheDir;

public FileCache(Context context){
//找一个用来缓存图片的路径
if (android.os.Environment.getExternalStorageState().equals(android.os.Environment.MEDIA_MOUNTED))
cacheDir=new File(android.os.Environment.getExternalStorageDirectory(),"LazyList");
else
cacheDir=context.getCacheDir();
if(!cacheDir.exists())
cacheDir.mkdirs();
}

public File getFile(String url){

String filename=String.valueOf(url.hashCode());
File f = new File(cacheDir, filename);
return f;

}

public void clear(){
File[] files=cacheDir.listFiles();
if(files==null)
return;
for(File f:files)
f.delete();
}

}

MemoryCache.java

package com.example.wjy329.ufo.Tools;

/**
* Created by wjy32 on 2016/3/2.
*/
import android.graphics.Bitmap;

import java.lang.ref.SoftReference;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;

public class MemoryCache {
private Map<String, SoftReference<Bitmap>> cache=Collections.synchronizedMap(new HashMap<String, SoftReference<Bitmap>>());//软引用

public Bitmap get(String id){
if(!cache.containsKey(id))
return null;
SoftReference<Bitmap> ref=cache.get(id);
return ref.get();
}

public void put(String id, Bitmap bitmap){
cache.put(id, new SoftReference<Bitmap>(bitmap));
}

public void clear() {
cache.clear();
}
}

4.head.java 头条实体类

package com.example.wjy329.ufo.Bean;

import cn.bmob.v3.BmobObject;

/**
* Created by wjy329 on 2017/3/4.
*/

public class head extends BmobObject {
private String picture; //图片
private String describe; //描述
private String title; //标题

public String getPicture() {
return picture;
}

public void setPicture(String picture) {
this.picture = picture;
}

public String getDescribe() {
return describe;
}

public void setDescribe(String describe) {
this.describe = describe;
}

public String getTitle() {
return title;
}

public void setTitle(String title) {
this.title = title;
}
}

5.FirstFragment.java 头条主代码

package com.example.wjy329.ufo.fragment;

import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

import com.example.wjy329.ufo.Activity.InfoActivity;
import com.example.wjy329.ufo.Adapter.HeadAdapter;
import com.example.wjy329.ufo.Bean.head;
import com.example.wjy329.ufo.R;

import java.util.List;
import java.util.Map;

import cn.bmob.v3.Bmob;
import cn.bmob.v3.BmobQuery;
import cn.bmob.v3.exception.BmobException;
import cn.bmob.v3.listener.FindListener;

import static cn.bmob.v3.Bmob.getApplicationContext;

/**
* Created by wjy329 on 2017/2/25.
*/

public class FirstFragment extends Fragment{
ListView listView;
HeadAdapter adapter;
@Override
public View onCreateView(LayoutInflater inflater,  ViewGroup container,  Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.list_head, container, false);
//Bmob应用的key
Bmob.initialize(this.getActivity(),"618f5d7ccf1b0dc170e0effbfd5dabae");
listView = (ListView) view.findViewById(R.id.list_head);
//Bmob查询方法
BmobQuery<head> query =new BmobQuery<head>();
query.order("-createdAt");
query.findObjects(new FindListener<head>() {
@Override
public void done(List<head> list, BmobException e) {
if(e ==null) {
adapter = new HeadAdapter(getActivity(), list);
listView.setAdapter(adapter);
}else{
Log.i("bmob","失败："+e.getMessage()+","+e.getErrorCode());
Toast.makeText(getApplicationContext(), "网络连接失败，请检查网络",
Toast.LENGTH_SHORT).show();
}
}
});
//item点击事件
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> adapterView, View view, int position, long id) {
head data = (head) listView.getAdapter().getItem(position);
Bundle bundle =new Bundle();
bundle.putString("title",data.getTitle());
bundle.putString("content",data.getDescribe());
Intent intent = new Intent(getActivity(), InfoActivity.class);
intent.putExtras(bundle);
startActivity(intent);
}
});
return view;
}
}

6.InfoActivity.java 详细信息加载页面，获取intent的传值

package com.example.wjy329.ufo.Activity;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v7.widget.Toolbar;
import android.view.MenuItem;
import android.widget.Button;
import android.widget.TextView;

import com.example.wjy329.ufo.R;
import com.example.wjy329.ufo.fragment.FirstFragment;

/**
* Created by wjy329 on 2017/3/9.
*/

public class InfoActivity extends Activity {
TextView infoTitle_tv;
TextView infoContent_tv;
Toolbar toolbar;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.info);
infoTitle_tv = (TextView) findViewById(R.id.InfoTitle);
infoContent_tv = (TextView) findViewById(R.id.InfoContent);
toolbar = (Toolbar) findViewById(R.id.toolbar_info);
Bundle b = getIntent().getExtras();
String info_title = b.getString("title");
String info_content = b.getString("content");
infoTitle_tv.setText(info_title);
infoContent_tv.setText(info_content);

toolbar.inflateMenu(R.menu.toolbar_menu_info);
toolbar.setOnMenuItemClickListener(new Toolbar.OnMenuItemClickListener(){

@Override
public boolean onMenuItemClick(MenuItem item) {
int menuItemId = item.getItemId();
if(menuItemId == R.id.action_home){
finish();
}
return  true;
}
});
}
}

这样就完成了头条的加载，可以从Bmob中更新数据，显示在app上。灵异事件和未解之谜的实现和头条一样，只需稍作修改，这里不再记录。下一篇会记录社区功能的实现。

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