記得新增intenet許可權,和sdcard的讀寫許可權

public class MainActivity extends AppCompatActivity {
    private String url = "具體下載新的apk的路勁";
    private int versionCode;
    private ProgressDialog dialog;
@Override
protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main
 
);
x.view().inject(this);
//得到當前的版本號,由於沒有釋出,所以無法得到新版本,暫時可以加頁可以不加
try {
            versionCode = getPackageManager().getPackageInfo(getPackageName(), 0)

.versionCode;
} catch (Exception e) {
            e.printStackTrace();
}

//發現新版本你的時候彈出對話方塊

        AlertDialog.Builder builder = new AlertDialog.Builder(this
 
);
builder.setTitle("發現新版本是否升級?");
builder.setPositiveButton("升級", new DialogInterface.OnClickListener() {
            @Override
public void onClick(DialogInterface dialog, int which) {
                initData();
}
        });
builder.setNegativeButton("取消", null);
builder.create().show();
}

    private void 
 
initData() {
        //設定檔案下載的位置和檔名字
String path = Environment.getExternalStorageDirectory().

getPath() + "/app.apk";
RequestParams params = new RequestParams(url);
//設定程式不重新給下載的檔案重新設定名字
params.setAutoRename(false);
//設定斷點續傳
params.setAutoResume(true);
//設定下載儲存的路徑
params.setSaveFilePath(path);
x.http().get(params, new Callback.ProgressCallback<File>() {
            @Override
public void onSuccess(File result) {
                Intent intent = new Intent(Intent.ACTION_VIEW);
//                intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);//可加可不加

//第一個引數是你下載的檔案,第二個是固定內容,可直接複製
intent.setDataAndType(Uri.fromFile(result), 

"application/vnd.android.package-archive");
startActivity(intent);
}

            @Override
public void onError(Throwable ex, boolean isOnCallback) {

            }

            @Override
public void onCancelled(CancelledException cex) {
            }

            @Override
public void onFinished() {
                if (dialog != null & dialog.getProgress() >= 100 && 

dialog.isShowing()) {
                    dialog.dismiss();
Toast.makeText(MainActivity.this, "升級完成", 

Toast.LENGTH_SHORT).show();
}
            }

            @Override
public void onWaiting() {

            }

            @Override
public void onStarted() {
                //初始化ProgressDiaLog
initProgressDiaLog();
}

            @Override
public void onLoading(long total, long current, boolean isDownloading) 

{
                //判斷是否是在下載中,可加也可不加
if (isDownloading) {
                    //算出來當前進度
int progress = (int) (current * 100 / total );
//把進度設定給progressBar
dialog.setProgress(progress);
}
            }
        });
}

    //建立進度條
private void initProgressDiaLog() {
        dialog = new ProgressDialog(this);
dialog.setTitle("正在下載中...");
dialog.setProgress(0);
dialog.setCancelable(false); //設定不可點選介面之外的區域讓對話方塊消失
        //設定進度條的樣式
dialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
dialog.show();
}
}