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android - 在 Android 免安装应用中下载文件

问题描述

我正在尝试通过 Instant 应用中的下载管理器下载文件：

Uri uri = Uri.parse("https://images.pexels.com/photos/67636/rose-blue-flower-rose-blooms-67636.jpeg?auto=compress&cs=tinysrgb&dpr=2&h=750&w=1260");

DownloadManager downloadManager = (DownloadManager) context.getSystemService(DOWNLOAD_SERVICE);
downloadManager.enqueue(new DownloadManager.Request(uri)
            .setTitle("Demo")
            .setDescription("Something useful. No, really.")
            .setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS,
                    "test.mp4"));

但得到一个例外：

  java.lang.IllegalStateException: Unable to create directory: /storage/emulated/0/Download
    at android.app.DownloadManager$Request.setDestinationInExternalPublicDir(DownloadManager.java:539)

有没有其他方法可以在免安装应用中下载文件？

标签： androidandroid-studioandroid-instant-apps

解决方案

问题似乎与 Android 6.0 中引入的 Android 运行时权限有关

当您的应用程序以 API 级别 23 为目标时，默认情况下所有权限都是错误的，您必须先请求权限对话框并批准权限，然后才能将其用于您的应用程序。

请求许可

public class RequestPermissionHandler {
    private Activity mActivity;
    private RequestPermissionListener mRequestPermissionListener;
    private int mRequestCode;

public void requestPermission(Activity activity, @NonNull String[] permissions, int requestCode,
        RequestPermissionListener listener) {
    mActivity = activity;
    mRequestCode = requestCode;
    mRequestPermissionListener = listener;

    if (!needRequestRuntimePermissions()) {
        mRequestPermissionListener.onSuccess();
        return;
    }
    requestUnGrantedPermissions(permissions, requestCode);
}

private boolean needRequestRuntimePermissions() {
    return Build.VERSION.SDK_INT >= Build.VERSION_CODES.M;
}

private void requestUnGrantedPermissions(String[] permissions, int requestCode) {
    String[] unGrantedPermissions = findUnGrantedPermissions(permissions);
    if (unGrantedPermissions.length == 0) {
        mRequestPermissionListener.onSuccess();
        return;
    }
    ActivityCompat.requestPermissions(mActivity, unGrantedPermissions, requestCode);
}

private boolean isPermissionGranted(String permission) {
    return ActivityCompat.checkSelfPermission(mActivity, permission)
            == PackageManager.PERMISSION_GRANTED;
}

private String[] findUnGrantedPermissions(String[] permissions) {
    List<String> unGrantedPermissionList = new ArrayList<>();
    for (String permission : permissions) {
        if (!isPermissionGranted(permission)) {
            unGrantedPermissionList.add(permission);
        }
    }
    return unGrantedPermissionList.toArray(new String[0]);
}

public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions,
        @NonNull int[] grantResults) {
    if (requestCode == mRequestCode) {
        if (grantResults.length > 0) {
            for (int grantResult : grantResults) {
                if (grantResult != PackageManager.PERMISSION_GRANTED) {
                    mRequestPermissionListener.onFailed();
                    return;
                }
            }
            mRequestPermissionListener.onSuccess();
        } else {
            mRequestPermissionListener.onFailed();
        }
    }
}

public interface RequestPermissionListener {
    void onSuccess();

    void onFailed();
}

像这样在活动中使用：

public class MainActivity extends AppCompatActivity {
    private RequestPermissionHandler mRequestPermissionHandler;

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

        findViewById(R.id.button).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                handleButtonClicked();
            }
        });
    }

    private void handleButtonClicked(){
        mRequestPermissionHandler.requestPermission(this, new String[] {
                Manifest.permission.RECEIVE_SMS, Manifest.permission.READ_EXTERNAL_STORAGE
        }, 123, new RequestPermissionHandler.RequestPermissionListener() {
            @Override
            public void onSuccess() {
                Toast.makeText(MainActivity.this, "request permission success", Toast.LENGTH_SHORT).show();
            }

            @Override
            public void onFailed() {
                Toast.makeText(MainActivity.this, "request permission failed", Toast.LENGTH_SHORT).show();
            }
        });

    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions,
            @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        mRequestPermissionHandler.onRequestPermissionsResult(requestCode, permissions,
                grantResults);
    }
}

并且不要忘记将其添加到您的manifest

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

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