断点续传与单例模式详解-优快云博客

本文链接：https://blog.youkuaiyun.com/Wandering_sea/article/details/102846214

@[toc] 断点续传和单例

断点续传

activity

package com.example.day01_homework;

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.view.View;
import android.widget.AdapterView;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.ProgressBar;
import android.widget.Toast;

import java.io.File;
import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {
    private ListView listView;
    private ProgressBar progressList;
    private MyAdapter adapter;
    private String path = "http://www.qubaobei.com/ios/cf/dish_list.php?stage_id=1&limit=20&page=1";
    private List<Food.DataBean> list = new ArrayList<>();
    private String url = "/storage/emulated/0/Pictures/";
    public static long all = 0;
    private String path1 = "";

    private Handler handler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            if (msg.what == 120) {
                int len = (int) msg.obj;
                progressList.setProgress(len);
                if (len == 100) {
                    progressList.setVisibility(View.GONE);
                    Toast.makeText(MainActivity.this, "下载完成", Toast.LENGTH_SHORT).show();
                }
            }

        }
    };


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            requestPermissions(new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE, Manifest.permission.READ_EXTERNAL_STORAGE}, 110);
        }

        initview();
        loadFromNet();
    }

    private void loadFromNet() {
        new MyAsynctask(list, adapter).execute(path);
    }

    private void initview() {
        listView = (ListView) findViewById(R.id.list_view);
        progressList = (ProgressBar) findViewById(R.id.progress_list);


        adapter = new MyAdapter(list, this);
        listView.setAdapter(adapter);

        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, final int position, long id) {
                path1 = url + position + ".jpg";
                File file = new File(path1);
                if (file.exists()) {
                    Toast.makeText(MainActivity.this, "图片已存在", Toast.LENGTH_SHORT).show();
                } else {
                    Toast.makeText(MainActivity.this, "图片不存在", Toast.LENGTH_SHORT).show();

                    AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);
                    builder.setTitle("友情提示！");
                    builder.setMessage("是否下载该图片");
                    builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialog, int which) {
                        }
                    });
                    builder.setPositiveButton("Allow", new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialog, int which) {
                            progressList.setVisibility(View.VISIBLE);
                            String pic = list.get(position).getPic();
                            new MyThread(pic, path1, handler).start();

                        }
                    });
                    AlertDialog dialog = builder.create();
                    dialog.show();

                }
            }


        });

    }
}

子线程

package com.example.day01_homework;

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;

class MyThread extends Thread {
    private String str_url;
    private String path;
    private Handler handler;


    public MyThread(String str_url, String path, Handler handler) {
        this.str_url = str_url;
        this.path = path;
        this.handler = handler;
    }

    private long end;
    private long start;


    @Override
    public void run() {
        super.run();
        try {
            URL url = new URL(str_url);
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            connection.setReadTimeout(3 * 1000);
            connection.setConnectTimeout(3 * 1000);
            connection.connect();

            if (connection.getResponseCode() == 200) {
                //获取总长度
                end = connection.getContentLength();
//                MainActivity.all = end;
                Log.d("TAG", "end: " + end);
            }
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        //第二次 设置请求头

        File file = new File(path);
        if (file.exists()) {
            start = file.length();
        } else {
            start = 0;
        }
        Log.d("TAG", "start: " + start);

        try {
            URL url = new URL(str_url);
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            connection.setReadTimeout(3 * 1000);
            connection.setConnectTimeout(3 * 1000);
            connection.setRequestProperty("Range", "bytes=" + start + "-" + end);
            connection.connect();

            if (connection.getResponseCode() == 206) {
                InputStream inputStream = connection.getInputStream();
                RandomAccessFile randomAccessFile = new RandomAccessFile(path, "rw");
                randomAccessFile.seek(start);
                int len = 0;
                byte[] bytes = new byte[1024];
                long count = start;
                while ((len = inputStream.read(bytes)) != -1) {
                    randomAccessFile.write(bytes, 0, len);
                    count += len;
                    int progress = (int) ((count * 100) / end);
                    Log.d("TAG", "run: " + progress);

                    Message obtain = Message.obtain();
                    obtain.what = 120;
                    obtain.obj = progress;
                    handler.sendMessage(obtain);
                }
            }

        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

    }
}

单例懒汉

package com.example.day01_homework;

public class TestUtils2 {

    private TestUtils2() {
    }

    private static TestUtils2 testUtils2 = null;

    public static TestUtils2 getInstance() {
        if (testUtils2 == null) {
            synchronized (Object.class) {
                if (testUtils2 == null) {
                    testUtils2 = new TestUtils2();
                }
            }
        }
        return testUtils2;
    }
}


package com.example.day01_homework;

public class Teest02 {

    public void test() {
        TestUtils2 instance1 = TestUtils2.getInstance();
        TestUtils2 instance2 = TestUtils2.getInstance();

        if (instance1.equals(instance2)) {
            System.out.println("1346789");
        } else {
            System.out.println("987654321");
        }
    }

}

饿汉

package com.example.day01_homework;

public class TestUtils {

    private TestUtils() {
    }

    private static TestUtils testUtils = new TestUtils();

    public static TestUtils getInstance() {
        return testUtils;
    }

}

package com.example.day01_homework;

public class single_e {

    public void getTest() {
        TestUtils utils1 = TestUtils.getInstance();
        TestUtils utils2 = TestUtils.getInstance();

        if (utils1.equals(utils2)) {
            System.out.println("1346789");
        } else {
            System.out.println("987654321");
        }


    }


}