授权权限下载文件

最新推荐文章于 2024-09-19 15:56:52 发布

Future_Master_L

最新推荐文章于 2024-09-19 15:56:52 发布

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本文介绍了一个简单的Android应用程序，用于演示如何实现文件下载功能，并请求必要的外部存储权限。通过使用Retrofit进行网络请求，文章详细展示了从用户点击按钮到下载完成整个流程的实现细节。

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用户授权写的权限下载文件


public class MainActivity extends AppCompatActivity {

    private final String TAG = "MainActivity";
    private final int CODE1 = 1;//读写sdcard权限


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button button = (Button) findViewById(R.id.btn);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                //版本适配
                //6.0及以上的设备
                if (Build.VERSION.SDK_INT > 22) {
                    //检查WRITE_EXTERNAL_STORAGE权限不等于授权状态的话,如果是授权状态直接下载
                    if (ContextCompat.checkSelfPermission(MainActivity.this, Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
                        // 用户拒绝了该权限，没有选中『不再询问』（Never ask again）,那么下次再次启动时，还会提示请求权限的对话框
                        if (ActivityCompat.shouldShowRequestPermissionRationale(MainActivity.this, Manifest.permission.WRITE_EXTERNAL_STORAGE)) {
                            Toast.makeText(MainActivity.this, "用户已拒绝", Toast.LENGTH_SHORT).show();
                        } else {
                            ActivityCompat.requestPermissions(MainActivity.this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, CODE1);
                        }

                    } else {
                        download();
                    }
                }
            }
        });
    }

    /**
     * 用户选择允许或拒绝后，会回调onRequestPermissionsResult方法, 该方法类似于onActivityResult
     */
    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        switch (requestCode) {
            case CODE1:
                //授权状态结果已经授权
                if (grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                    download();
                } else {
                    if (ActivityCompat.shouldShowRequestPermissionRationale(this, Manifest.permission.WRITE_EXTERNAL_STORAGE)) {

                        Toast.makeText(this, "用户已拒绝", Toast.LENGTH_SHORT).show();
                        //做自己的逻辑，比如新建弹窗跳转到权限设置页面，或者重新运行请求权限方式
                    } else {
                        ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, CODE1);
                    }
                }
                break;

        }
    }

    /**
     * 下载文件
     */
    private void download() {
        Log.d(TAG, "download: 开始下载+++++++++++++++");

        Retrofit build = new Retrofit.Builder()
                .addCallAdapterFactory(RxJava2CallAdapterFactory.create())
                .baseUrl(Constants.BASE_URL)
                .build();
        ApiService apiService = build.create(ApiService.class);
        apiService.download().subscribeOn(Schedulers.io()).observeOn(Schedulers.io())
                .subscribe(new Consumer<ResponseBody>() {
                    @Override
                    public void accept(ResponseBody responseBody) throws Exception {
                        //判断SD卡状态为MEDIA_MOUNTED时/mnt/sdcard目录是否可读可写
                        if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {
                            String path = Environment.getExternalStorageDirectory() + File.separator + "master/";
                            File file = new File(path);
                            //master文件是否存在,不存在则创建
                            if (!file.exists()) {
                                file.mkdirs();
                            }
                            File dirFile = new File(file, "download.apk");
                            if (!dirFile.exists()) {
                                dirFile.createNewFile();
                            }

                            InputStream inputStream = responseBody.byteStream();
                            FileOutputStream fileOutputStream = new FileOutputStream(dirFile);
                            int length = 0;
                            byte[] bytes = new byte[2048];
                            while ((length = inputStream.read(bytes)) != -1) {
                                Log.d(TAG, "download: ==="+length);
                                fileOutputStream.write(bytes, 0, length);
                                fileOutputStream.flush();
                            }
                            Log.d(TAG, "download: 下载完毕+++++++++++++++");
                            fileOutputStream.close();
                            inputStream.close();
                        }
                    }
                }, new Consumer<Throwable>() {
                    @Override
                    public void accept(Throwable throwable) throws Exception {
                        //异常处理
                    }
                });
    }
}

public interface ApiService {
    @GET("version/file.apk")
    @Streaming
    Observable<ResponseBody> download();
}

public class Constants {
    public static final String BASE_URL = "https://www.zhaoapi.cn/";
}