PackageInfo pinfo = null;
try {
    pinfo = getPackageManager().getPackageInfo(getPackageName(), 0);
}
catch (PackageManager.NameNotFoundException e) {
    e.printStackTrace();
}
int versionNumber = pinfo.versionCode;
String versionName = pinfo.versionName;

如果您只需要版本名称，请稍微缩短版本。

try{
    String versionName = context.getPackageManager()
    .getPackageInfo(context.getPackageName(), 0).versionName;
} catch (PackageManager.NameNotFoundException e) {
        e.printStackTrace();
        return false;
}

package com.sqisland.android.versionview;

import android.app.Activity;
import android.content.pm.PackageInfo;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.widget.TextView;

public class MainActivity extends Activity {
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    TextView textViewversionName = (TextView) findViewById(R.id.text);

    try {
        PackageInfo packageInfo = getPackageManager().getPackageInfo(getPackageName(), 0);
        textViewversionName.setText(packageInfo.versionName);

    }
    catch (PackageManager.NameNotFoundException e) {

    }
  }
}

对于API 28（Android 9（Pie）），PackageInfo.versionCode已弃用，因此请使用以下代码：

Context context = getApplicationContext();
PackageManager manager = context.getPackageManager();
try {
    PackageInfo info = manager.getPackageInfo(context.getPackageName(), 0);
    myversionName = info.versionName;
    versionCode = (int) PackageInfoCompat.getLongVersionCode(info);
}
catch (PackageManager.NameNotFoundException e) {
    e.printStackTrace();
    myversionName = "Unknown-01";
}

try {
    PackageInfo packageInfo = getPackageManager().getPackageInfo(getPackageName(), 0);
    String versionName = packageInfo.versionName;
    int versionCode = packageInfo.versionCode;
    //binding.tvVersionCode.setText("v" + packageInfo.versionName);
}
catch (PackageManager.NameNotFoundException e) {
    e.printStackTrace();
}

版本名称：BuildConfig.version_name版本代码：BuildConfig.version_code