Android studio 45 下載mp3 歌曲並保存

用httpServer搭建http服務器

第一步activity-main.xml
    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="Button" />

第二步MainAtcivity.java
package com.example.downloadmp01;

import androidx.appcompat.app.AppCompatActivity;

import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

import java.io.BufferedInputStream;
import java.io.ByteArrayOutputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URL;
import java.net.URLConnection;

public class MainActivity extends AppCompatActivity {

    private int fileLength;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Button btn = findViewById(R.id.button);
        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // 響應事件
//                Toast.makeText(MainActivity.this,"測試按鈕",Toast.LENGTH_SHORT).show();
                new Thread(downloadRunn).start();

            }
        });

    }
    private Runnable downloadRunn = new  Runnable(){
        @Override
        public void run() {
            try {
                String filepath="/sdcard/Download/mmmmm20200602.mp3";
                String urlString="http://192.168.3.87:280/AA2020.mp3";
                OutputStream output = new FileOutputStream("/sdcard/Download/ANewthefile.mp3");
                URL url = new URL(urlString);
                URLConnection connection = url.openConnection();
                connection.connect();
                fileLength = connection.getContentLength();
                InputStream in = new BufferedInputStream(connection.getInputStream());
                byte[] arr = readStream(in);

                output.write(arr,0,fileLength);
                output.flush();
                output.close();

            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    };
    public  byte[] readStream(InputStream in) throws Exception{
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        byte data[] = new byte[1024];
        long total = 0;
        int count;
        while((count = in.read(data))!=-1){
            total+=count;
            bos.write(data,0,count);
        }
        bos.close();
        in.close();
        return bos.toByteArray();
    }
}

第三步權限
 <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />

第四步到手機端app管理添加sdcard 存儲權限。
運行