UpdateNode provides an API for Android to install APK packages from inside another App. You can just define your Update online and integrate the API into your App - that's it. Currently the API is in Beta state, but you can already do some tests yourself. Beside that, UpdateNode offers also displaying messages though the system - pretty useful if you want to tell something important to your users. I am part of the client dev team and am using at least the message functionality for my own Android App.

这里介绍了如何集成API

我只是想分享一个事实，我的apk文件保存到我的应用程序“数据”目录，我需要更改apk文件的权限，使其成为世界可读的，以便允许它以这种方式安装，否则系统会抛出“解析错误:解析包存在问题”;所以使用@Horaceman的解决方案，使:

File file = new File(dir, "App.apk");
file.setReadable(true, false);
Intent intent = new Intent(Intent.ACTION_VIEW);
intent.setDataAndType(Uri.fromFile(file), "application/vnd.android.package-archive");
startActivity(intent);

为这个问题提供的解决方案都适用于23及以下的targetSdkVersion。然而，对于Android N，即API级别24及以上，它们不能工作并崩溃如下异常:

android.os.FileUriExposedException: file:///storage/emulated/0/... exposed beyond app through Intent.getData()

这是因为从Android 24开始，用于寻址下载文件的Uri已经改变。例如，一个名为appName.apk的安装文件存储在应用程序的主要外部文件系统上，包名为com.example.test

file:///storage/emulated/0/Android/data/com.example.test/files/appName.apk

适用于API 23及以下，而类似的

content://com.example.test.authorityStr/pathName/Android/data/com.example.test/files/appName.apk

适用于API 24或以上。

关于这方面的更多细节可以在这里找到，我不打算详细介绍。

要回答24及以上版本的targetSdkVersion的问题，必须遵循以下步骤: 将以下内容添加到AndroidManifest.xml:

<application
        android:allowBackup="true"
        android:label="@string/app_name">
        <provider
            android:name="android.support.v4.content.FileProvider"
            android:authorities="${applicationId}.authorityStr"
            android:exported="false"
            android:grantUriPermissions="true">
            <meta-data
                android:name="android.support.FILE_PROVIDER_PATHS"
                android:resource="@xml/paths"/>
        </provider>
</application>

2. 将下面的paths.xml文件添加到src, main中的res的xml文件夹中:

<?xml version="1.0" encoding="utf-8"?>
<paths xmlns:android="http://schemas.android.com/apk/res/android">
    <external-path
        name="pathName"
        path="pathValue"/>
</paths>

pathName是上面示例内容uri示例中显示的，pathValue是系统上的实际路径。 放个"。"是个好主意如果您不想添加任何额外的子目录，则为上面的pathValue(不带引号)。

Write the following code to install the apk with the name appName.apk on the primary external filesystem: File directory = context.getExternalFilesDir(null); File file = new File(directory, fileName); Uri fileUri = Uri.fromFile(file); if (Build.VERSION.SDK_INT >= 24) { fileUri = FileProvider.getUriForFile(context, context.getPackageName(), file); } Intent intent = new Intent(Intent.ACTION_VIEW, fileUri); intent.putExtra(Intent.EXTRA_NOT_UNKNOWN_SOURCE, true); intent.setDataAndType(fileUri, "application/vnd.android" + ".package-archive"); intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK | Intent.FLAG_ACTIVITY_NEW_TASK); intent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION); context.startActivity(intent); activity.finish();

在外部文件系统上写入自己应用程序的私有目录时，也不需要任何权限。

我在这里写了一个AutoUpdate库，我使用了上面的方法。

只是一个扩展，如果有人需要一个库，那么这可能会有所帮助。感谢Raghav

首先在AndroidManifest.xml中添加以下行:

<uses-permission android:name="android.permission.INSTALL_PACKAGES"
    tools:ignore="ProtectedPermissions" />

然后使用以下代码安装apk:

File sdCard = Environment.getExternalStorageDirectory();
            String fileStr = sdCard.getAbsolutePath() + "/MyApp";// + "app-release.apk";
            File file = new File(fileStr, "TaghvimShamsi.apk");
            Intent promptInstall = new Intent(Intent.ACTION_VIEW).setDataAndType(Uri.fromFile(file),
                    "application/vnd.android.package-archive");
            startActivity(promptInstall);

不要忘记申请权限:

android.Manifest.permission.WRITE_EXTERNAL_STORAGE 
android.Manifest.permission.READ_EXTERNAL_STORAGE

在AndroidManifest.xml中添加提供商和权限:

<uses-permission android:name="android.permission.REQUEST_INSTALL_PACKAGES"/>
...
<application>
    ...
    <provider
        android:name="android.support.v4.content.FileProvider"
        android:authorities="${applicationId}"
        android:exported="false"
        android:grantUriPermissions="true">
        <meta-data
            android:name="android.support.FILE_PROVIDER_PATHS"
            android:resource="@xml/provider_paths"/>
    </provider>
</application>

创建XML文件提供程序res/ XML /provider_paths.xml

<?xml version="1.0" encoding="utf-8"?>
<paths xmlns:android="http://schemas.android.com/apk/res/android">
    <external-path
        name="external"
        path="." />
    <external-files-path
        name="external_files"
        path="." />
    <cache-path
        name="cache"
        path="." />
    <external-cache-path
        name="external_cache"
        path="." />
    <files-path
        name="files"
        path="." />
</paths>

使用下面的示例代码:

   public class InstallManagerApk extends AppCompatActivity {

    static final String NAME_APK_FILE = "some.apk";
    public static final int REQUEST_INSTALL = 0;

     @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // required permission:
        // android.Manifest.permission.WRITE_EXTERNAL_STORAGE 
        // android.Manifest.permission.READ_EXTERNAL_STORAGE

        installApk();

    }

    ...

    /**
     * Install APK File
     */
    private void installApk() {

        try {

            File filePath = Environment.getExternalStorageDirectory();// path to file apk
            File file = new File(filePath, LoadManagerApkFile.NAME_APK_FILE);

            Uri uri = getApkUri( file.getPath() ); // get Uri for  each SDK Android

            Intent intent = new Intent(Intent.ACTION_INSTALL_PACKAGE);
            intent.setData( uri );
            intent.setFlags( Intent.FLAG_GRANT_READ_URI_PERMISSION | Intent.FLAG_ACTIVITY_NEW_TASK );
            intent.putExtra(Intent.EXTRA_NOT_UNKNOWN_SOURCE, true);
            intent.putExtra(Intent.EXTRA_RETURN_RESULT, true);
            intent.putExtra(Intent.EXTRA_INSTALLER_PACKAGE_NAME, getApplicationInfo().packageName);

            if ( getPackageManager().queryIntentActivities(intent, 0 ) != null ) {// checked on start Activity

                startActivityForResult(intent, REQUEST_INSTALL);

            } else {
                throw new Exception("don`t start Activity.");
            }

        } catch ( Exception e ) {

            Log.i(TAG + ":InstallApk", "Failed installl APK file", e);
            Toast.makeText(getApplicationContext(), e.getMessage(), Toast.LENGTH_LONG)
                .show();

        }

    }

    /**
     * Returns a Uri pointing to the APK to install.
     */
    private Uri getApkUri(String path) {

        // Before N, a MODE_WORLD_READABLE file could be passed via the ACTION_INSTALL_PACKAGE
        // Intent. Since N, MODE_WORLD_READABLE files are forbidden, and a FileProvider is
        // recommended.
        boolean useFileProvider = Build.VERSION.SDK_INT >= Build.VERSION_CODES.N;

        String tempFilename = "tmp.apk";
        byte[] buffer = new byte[16384];
        int fileMode = useFileProvider ? Context.MODE_PRIVATE : Context.MODE_WORLD_READABLE;
        try (InputStream is = new FileInputStream(new File(path));
             FileOutputStream fout = openFileOutput(tempFilename, fileMode)) {

            int n;
            while ((n = is.read(buffer)) >= 0) {
                fout.write(buffer, 0, n);
            }

        } catch (IOException e) {
            Log.i(TAG + ":getApkUri", "Failed to write temporary APK file", e);
        }

        if (useFileProvider) {

            File toInstall = new File(this.getFilesDir(), tempFilename);
            return FileProvider.getUriForFile(this,  BuildConfig.APPLICATION_ID, toInstall);

        } else {

            return Uri.fromFile(getFileStreamPath(tempFilename));

        }

    }

    /**
     * Listener event on installation APK file
     */
    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);

        if(requestCode == REQUEST_INSTALL) {

            if (resultCode == Activity.RESULT_OK) {
                Toast.makeText(this,"Install succeeded!", Toast.LENGTH_SHORT).show();
            } else if (resultCode == Activity.RESULT_CANCELED) {
                Toast.makeText(this,"Install canceled!", Toast.LENGTH_SHORT).show();
            } else {
                Toast.makeText(this,"Install Failed!", Toast.LENGTH_SHORT).show();
            }

        }

    }

    ...

}