android 下载文件并显示下载进度

最新推荐文章于 2025-09-25 09:23:00 发布

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本文介绍如何在Android中实现文件下载，并在下载过程中显示进度条。内容涉及将下载操作放在后台线程中，使用DialogProgress布局更新进度，并提醒读者注意处理权限问题。

android 下载文件并显示下载进度

	private String fileSavePath=Environment.getExternalStorageDirectory() + "/";//保存文件的本地路径
    private String fileDownLoad_path="";//下载的URL
    private String mfileName="";//下载的文件名字
    private boolean mIsCancel = false;
    private int mProgress;
    private ProgressBar mProgressBar;
    private Dialog mDownloadDialog;

    private static final int DOWNLOADING = 1;
    private static final int DOWNLOAD_FINISH = 2;

 private Handler mUpdateProgressHandler = new Handler() {
        public void handleMessage(Message msg) {
            switch (msg.what) {
                case DOWNLOADING:
                    // 设置进度条
                    mProgressBar.setProgress(mProgress);
                    break;
                case DOWNLOAD_FINISH:
                    // 隐藏当前下载对话框
                    mDownloadDialog.dismiss();
            }
        }
    };

 /**
     * 显示正在下载的对话框
     */
    protected void showDownloadDialog() {
        AlertDialog.Builder builder = new AlertDialog.Builder(context);
        builder.setTitle("下载中");
        View view = LayoutInflater.from(context).inflate(R.layout.dialog_progress, null);
        mProgressBar = (ProgressBar) view.findViewById(R.id.id_progress);
        builder.setView(view);

        builder.setNegativeButton("取消", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                // 隐藏当前对话框
                dialog.dismiss();
                // 设置下载状态为取消
                mIsCancel = true;
            }
        });

        mDownloadDialog = builder.create();
        mDownloadDialog.show();

        // 下载文件
        downloadFile();
    }

写下载放在线程中

 private void downloadFile() {
        new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {
                        File dir = new File(fileSavePath);
                        if (!dir.exists()){
                            dir.mkdirs();
                        }
                        // 下载文件
                        HttpURLConnection conn = (HttpURLConnection) new URL(fileDownLoad_path).openConnection();
                        conn.connect();
                        InputStream is = conn.getInputStream();
                        int length = conn.getContentLength();

                        File apkFile = new File(fileSavePath, mfileName);
                        FileOutputStream fos = new FileOutputStream(apkFile);

                        int count = 0;
                        byte[] buffer = new byte[1024];
                        while (!mIsCancel) {
                            int numread = is.read(buffer);
                            count += numread;
                            // 计算进度条当前位置
                            mProgress = (int) (((float) count / length) * 100);
                            // 更新进度条
                            mUpdateProgressHandler.sendEmptyMessage(DOWNLOADING);

                           // 下载完成
                            if (numread < 0) {
                                mUpdateProgressHandler.sendEmptyMessage(DOWNLOAD_FINISH);
                                break;
                            }
                            fos.write(buffer, 0, numread);
                        }
                        fos.close();
                        is.close();
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }).start();
    }

dialogprogress的布局文件

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    tools:context=".MainActivity" >

    <ProgressBar
        android:id="@+id/id_progress"
        style="?android:attr/progressBarStyleHorizontal"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

</LinearLayout>

应该不缺少文件了。注意权限问题。