单例模式 断点续传

Day10.31作业

单例模式（饿汉式和懒汉式）断点续传布局item的布局网络请求写一个JavaBean的类适配器异步ThreadMain

单例模式（饿汉式和懒汉式）

package com.example.app2; public class Utils { //饿汉式 // public Utils() { // } // private static Utils utils = new Utils(); // public static Utils getInstance(){ // return utils; // } //懒汉式 public Utils() { } private static Utils utils = null; public static Utils getInstance(){ if (utils == null){ synchronized (Object.class){ if (utils == null){ utils = new Utils(); } } } return utils; } }

断点续传

布局

<?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" tools:context=".MainActivity"> <ListView android:id="@+id/lv" android:layout_width="match_parent" android:layout_height="match_parent"></ListView> <SeekBar android:id="@+id/bar" android:layout_width="match_parent" android:layout_height="20sp" android:layout_centerInParent="true" android:visibility="gone"/> </RelativeLayout>

item的布局

<?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent"> <ImageView android:id="@+id/zz" android:layout_width="100dp" android:layout_height="100dp" android:src="@mipmap/ic_launcher" android:layout_centerInParent="true"/> </RelativeLayout>

网络请求

package com.example.day1031; import android.util.Log; import java.io.ByteArrayOutputStream; import java.io.IOException; import java.io.InputStream; import java.net.HttpURLConnection; import java.net.MalformedURLException; import java.net.URL; import java.net.URLConnection; public class Httputils { private static final String TAG = "Httputils"; public static String geturl(String s){ try { URL url = new URL(s); HttpURLConnection connection = (HttpURLConnection) url.openConnection(); connection.connect(); Log.i(TAG, "geturl: "+connection.getResponseCode()); if (connection.getResponseCode() == 200){ ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream(); InputStream inputStream = connection.getInputStream(); int len = 0; byte[] bytes = new byte[1024]; while ((len = inputStream.read(bytes))!=-1){ byteArrayOutputStream.write(bytes,0,len); } return byteArrayOutputStream.toString(); } } catch (MalformedURLException e) { e.printStackTrace(); } catch (IOException e) { } return null; } }

写一个JavaBean的类

适配器

package com.example.day1031; import android.content.Context; import android.util.Log; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.BaseAdapter; import android.widget.ImageView; import com.bumptech.glide.Glide; import java.util.List; public class MyAdapter extends BaseAdapter { private static final String TAG = "MyAdapter"; private List<JavaBean.DataBean> list; private Context context; private LayoutInflater layoutInflater; public MyAdapter(List<JavaBean.DataBean> list, Context context) { this.list = list; this.context = context; layoutInflater = LayoutInflater.from(context); } @Override public int getCount() { return list.size(); } @Override public Object getItem(int position) { return list.get(position); } @Override public long getItemId(int position) { return position; } @Override public View getView(int position, View convertView, ViewGroup parent) { ViewHolder holder = null; if (convertView == null){ holder = new ViewHolder(); convertView = layoutInflater.inflate(R.layout.layout_item,null); holder.iv = convertView.findViewById(R.id.zz); convertView.setTag(holder); }else { holder = (ViewHolder) convertView.getTag(); } Glide.with(context).load(list.get(position).getPic()).into(holder.iv); return convertView; } class ViewHolder{ ImageView iv; } }

异步

package com.example.day1031; import android.os.AsyncTask; import android.util.Log; import com.google.gson.Gson; import java.util.List; public class MyAsync extends AsyncTask<String,Void, List<JavaBean.DataBean>> { private static final String TAG = "MyAsync"; private List<JavaBean.DataBean> list ; private MyAdapter myAdapter; public MyAsync(List<JavaBean.DataBean> list, MyAdapter myAdapter) { this.list = list; this.myAdapter = myAdapter; } @Override protected List<JavaBean.DataBean> doInBackground(String... strings) { String geturl = Httputils.geturl(strings[0]); Log.i(TAG, "doInBackground: "+geturl); if (geturl != null){ JavaBean javaBean = new Gson().fromJson(geturl, JavaBean.class); List<JavaBean.DataBean> data = javaBean.getData(); return data; } return null; } @Override protected void onPostExecute(List<JavaBean.DataBean> dataBeans) { super.onPostExecute(dataBeans); if (dataBeans != null){ list.addAll(dataBeans); myAdapter.notifyDataSetChanged(); Log.i(TAG, "onPostExecute: "+list.get(1).getTitle()); } } }

Thread

package com.example.day1031; import android.os.Handler; import android.os.Message; import android.util.Log; import java.io.File; import java.io.IOException; import java.io.InputStream; import java.io.RandomAccessFile; import java.net.HttpURLConnection; import java.net.MalformedURLException; import java.net.URL; import java.net.URLConnection; public class MyThread extends Thread { private static final String TAG = "MyThread"; private String url ; private String path; private Handler handler; public MyThread(String url, String path, Handler handler) { this.url = url; this.path = path; this.handler = handler; } private long start = 0; private long end; @Override public void run() { //第一次请求 try { URL url = new URL(this.url); HttpURLConnection connection = (HttpURLConnection) url.openConnection(); connection.connect(); Log.i(TAG, "run: "+connection.getResponseCode()); if (connection.getResponseCode() == 200){ end = connection.getContentLength(); } } catch (MalformedURLException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } File file = new File(path); if (file.exists()){ start = file.length(); }else { start = 0; } //第二次请求 try { URL url = new URL(this.url); HttpURLConnection connection = (HttpURLConnection) url.openConnection(); connection.connect(); Log.i(TAG, "run: "+connection.getResponseCode()); if (connection.getResponseCode() == 200){ if (start == end){ handler.sendEmptyMessage(200); }else{ InputStream inputStream = connection.getInputStream(); RandomAccessFile rw = new RandomAccessFile(path, "rw"); rw.seek(start); long context = start; int len = 0; byte[] bytes = new byte[1024]; while ((len = inputStream.read(bytes))!=-1){ rw.write(bytes,0,len); context+=len; int progress = (int) (context*100/end); Message message = new Message(); message.what = 100; message.arg1 = progress; handler.sendMessage(message); } } } } catch (MalformedURLException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } } }

Main

package com.example.day1031; import android.Manifest; import android.content.DialogInterface; import android.os.Build; import android.os.Handler; import android.os.Message; import android.support.v7.app.AlertDialog; import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import android.util.Log; import android.view.View; import android.widget.AdapterView; import android.widget.ListView; import android.widget.SeekBar; import android.widget.Toast; import java.util.ArrayList; import java.util.List; public class MainActivity extends AppCompatActivity { private static final String TAG = "MainActivity"; private ListView lv; private SeekBar bar; private List<JavaBean.DataBean> list = new ArrayList<>(); private String url="http://www.qubaobei.com/ios/cf/dish_list.php?stage_id=1&limit=10&page=1"; private Handler handler = new Handler(){ @Override public void handleMessage(Message msg) { if (msg.what == 100){ bar.setVisibility(View.VISIBLE); int arg1 = msg.arg1; bar.setProgress(arg1); if (arg1 == bar.getMax()){ bar.setVisibility(View.GONE); } } if (msg.what == 200){ Toast.makeText(MainActivity.this, "已经下载", Toast.LENGTH_SHORT).show(); } } }; private MyAdapter myAdapter; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); lv = (ListView) findViewById(R.id.lv); bar = (SeekBar) findViewById(R.id.bar); //获取权限 if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M){ requestPermissions(new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE},100); } //设置适配器 myAdapter = new MyAdapter(list,this); lv.setAdapter(myAdapter); //进行异步 Async(); //设置点击事件 lv.setOnItemClickListener(new AdapterView.OnItemClickListener() { @Override public void onItemClick(AdapterView<?> parent, View view, final int position, long id) { AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this); builder.setTitle("提示"); builder.setMessage("是否下载这张图片"); builder.setPositiveButton("确定", new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { new MyThread(list.get(position).getPic(),"/storage/emulated/0/Movies/"+"pic"+position+".jpg",handler).start(); } }); builder.setNegativeButton("取消", new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { Toast.makeText(MainActivity.this, "取消", Toast.LENGTH_SHORT).show(); } }); AlertDialog alertDialog = builder.create(); alertDialog.show(); } }); } private void Async() { new MyAsync(list,myAdapter).execute(url); } }