Android studio 53 文件下载

第一步MainActivity.java
package com.example.myoo;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends Activity {

//android:usesCleartextTraffic="true"   这句话非常重要

    private Button btnsave;
    private EditText editurl;

    Handler handler = new Handler()
    {
        public void handleMessage(android.os.Message msg)
        {
            if(msg.what == 0x123)
            {
                Toast.makeText(getApplicationContext(), "开始下载", Toast.LENGTH_SHORT).show();
            }
        };
    };


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

        btnsave = (Button) findViewById(R.id.btnsave);
        editurl = (EditText) findViewById(R.id.editurl);

        btnsave.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                new Thread()
                {
                    @Override
                    public void run() {
                        String path = editurl.getText().toString();
                        try {
                            DownLoadService.downLoad(path, MainActivity.this);
                        } catch (Exception e) {e.printStackTrace();}
                        handler.sendEmptyMessage(0x123);
                    }
                }.start();

            }
        });

    }
}

第二步activity-main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="请输入图片的网络地址" />
    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/editurl"
        android:text="http://10.13.20.32:8080/Test/db.zip"
        />
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/btnsave"
        android:text="缓存文件"
        />

</LinearLayout>

第三步 androidManifest.xml
    <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" />

        android:usesCleartextTraffic="true"


第四步：
package com.example.myoo;

import java.io.InputStream;
import java.io.OutputStream;
import java.net.URL;

import android.content.Context;
import android.widget.Toast;

public class DownLoadService {

    public static void downLoad(String path,Context context)throws Exception
    {
        URL url = new URL(path);
        InputStream is = url.openStream();
        //截取最后的文件名
        String end = path.substring(path.lastIndexOf("."));
        //打开手机对应的输出流,输出到文件中
        OutputStream os = context.openFileOutput("Cache_"+System.currentTimeMillis()+end, Context.MODE_PRIVATE);
        byte[] buffer = new byte[1024];
        int len = 0;
        //从输入六中读取数据,读到缓冲区中
        while((len = is.read(buffer)) > 0)
        {
            os.write(buffer,0,len);
        }
        //关闭输入输出流
        is.close();
        os.close();
    }

}