20160414_jeffrey - silenceuncrio/diary GitHub Wiki

package com.bignerdranch.android.useasynctask;

import android.app.ProgressDialog;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.ImageView;

import java.io.BufferedInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;

public class MainActivity extends AppCompatActivity {

    private ImageView imageView;

    // 圖片地址
    private final String url = "http://www.photowant.com/photo101/fhen02381991/pl_fhen02381991_0018.jpg";
    //顯示進度
    private ProgressDialog pDialog;


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

        //用來顯示進度
        pDialog = new ProgressDialog(this);
        pDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
        pDialog.setMessage("Loading...");
        pDialog.setMax(100);

        imageView = (ImageView) findViewById(R.id.movie_image);

        //執行 Task
        new ImageDownloadTask().execute(url);

    }



    public class ImageDownloadTask extends AsyncTask<String,Integer,Bitmap> {

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            pDialog.show();
        }

        @Override
        protected Bitmap doInBackground(String... urls) {

            HttpURLConnection connection = null;

            Bitmap bitmap = null;

            try {

                URL url = new URL(urls[0]);

                connection = (HttpURLConnection) url.openConnection();

                InputStream in = new BufferedInputStream(connection.getInputStream());

                bitmap = BitmapFactory.decodeStream(in);

                //獲取文件流大小, 用於更新進度
                int length = connection.getContentLength();
                int len = 0, total_length = 0, value = 0;
                byte[] data = new byte[1024];

                while ( (len = in.read(data)) != -1) {
                    total_length += len;
                    value = (int)( (total_length/(float)length)*100);
                    //調用update函數, 更新進度
                    publishProgress(value);

                }


            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                if (connection != null) {
                    connection.disconnect();
                }
            }

            return bitmap;

        }

        @Override
        protected void onProgressUpdate(Integer... values) {
            super.onProgressUpdate(values);
            pDialog.setProgress(values[0]);
        }

        @Override
        protected void onPostExecute(Bitmap bitmap) {
            if (pDialog != null) {
                pDialog.dismiss();
            }
            pDialog = null;
            // 將Bitmap填充進ImageView
            imageView.setImageBitmap(bitmap);
        }

    }

}