HiddenApiTestApp/java/com/google/android/hiddenapi/testapp/MainActivity.java

package com.google.android.hiddenapi.testapp;

import android.app.Activity;
import android.os.Bundle;
import android.os.StrictMode;
import android.os.strictmode.Violation;
import android.text.TextUtils;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.TextView;
import dalvik.system.VMRuntime;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

public class MainActivity extends Activity implements OnClickListener {

  enum AppStrictMode {
    OFF,
    LOG,
    DEATH,
    CALLBACK;
    private static AppStrictMode[] vals = values();
    public AppStrictMode next()
    {
      return vals[(this.ordinal()+1) % vals.length];
    }
  }

  private final StrictMode.OnVmViolationListener mViolationListener = (v) -> onVmViolation(v);

  private TextView mTextView;
  private TextView mCurrentStrictMode;
  private TextView mStrictModeText;

  private AppStrictMode mCurrentMode = AppStrictMode.OFF;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    mTextView = findViewById(R.id.textView);
    mCurrentStrictMode = findViewById(R.id.strict_mode);
    mStrictModeText = findViewById(R.id.strict_mode_text);

    setAllButtonClickListeners(findViewById(R.id.layout));

    setStrictMode(AppStrictMode.OFF);
  }

  private void setAllButtonClickListeners(View v) {
    if (v instanceof Button) {
      v.setOnClickListener(this);
    } else if (v instanceof ViewGroup) {
      ViewGroup vg = (ViewGroup) v;
      for (int i = 0; i < vg.getChildCount(); i++) {
        setAllButtonClickListeners(vg.getChildAt(i));
      }
    }
  }

  private void onVmViolation(Violation v) {
    setStrictModeText(toString(v));
  }

  private void setStrictModeText(String s) {
    if (TextUtils.isEmpty(s)) {
      mStrictModeText.setText("");
      mStrictModeText.setVisibility(View.GONE);
    } else {
      mStrictModeText.setText(s);
      mStrictModeText.setVisibility(View.VISIBLE);
    }

  }
  private void setStrictMode(AppStrictMode mode) {
    StrictMode.VmPolicy policy;
    switch (mode) {
      case OFF:
        policy = new StrictMode.VmPolicy.Builder().permitNonSdkApiUsage().build();
        break;
      case LOG:
        policy = new StrictMode.VmPolicy.Builder().detectNonSdkApiUsage().penaltyLog().build();
        break;
      case DEATH:
        policy = new StrictMode.VmPolicy.Builder().detectNonSdkApiUsage().penaltyDeath().build();
        break;
      case CALLBACK:
        policy = new StrictMode.VmPolicy.Builder()
            .detectNonSdkApiUsage()
            .penaltyListener(r -> mStrictModeText.post(r), mViolationListener)
            .build();
        break;
      default:
        return;
    }
    mCurrentMode = mode;
    StrictMode.setVmPolicy(policy);
    mCurrentStrictMode.setText("StrictMode: " + mode);
  }

  @Override
  public void onClick(View view) {
    setStrictModeText(null);
    switch (view.getId()) {
      case R.id.disable_checks_reflection:
        try {
          tryDisableApiChecksReflectively();
          mTextView.setText("Ok \uD83D\uDE00");
        } catch (Exception e) {
          handleException(e);
        }
        break;
      case R.id.disable_checks_linking:
        try {
          tryDisableApiChecksLinking();
        } catch (LinkageError e) {
          handleException(e);
        }
        break;
      case R.id.strict_mode:
        setStrictMode(mCurrentMode.next());
        break;
      default:
        String name = ((TextView) view).getText().toString();
        accessActivityMember(name);
        break;
    }
  }

  private void accessActivityMember(String name) {
    try {
      Field f = Activity.class.getDeclaredField(name);
      f.setAccessible(true);
      Object o = f.get(this);
      mTextView.setText(String.format("%s: %s", name, o == null ? "null" : o.toString()));
    } catch (NoSuchFieldException e) {
      handleException(e);
    } catch (IllegalAccessException e) {
      handleException(e);
    }
  }

  private void handleException(Throwable e) {
    Log.e(getClass().getSimpleName(), "Failed", e);
    mTextView.setText(toString(e));
  }

  private static String toString(Throwable t) {
    StringWriter s = new StringWriter();
    t.printStackTrace(new PrintWriter(s));
    return s.toString();
  }

  private static void tryDisableApiChecksReflectively()
          throws ClassNotFoundException, NoSuchMethodException, InvocationTargetException,
          IllegalAccessException {
    Class vmRuntimeClass = Class.forName("dalvik.system.VMRuntime");
    Method getRuntime = vmRuntimeClass.getDeclaredMethod("getRuntime");
    Object vmRuntime =  getRuntime.invoke(null);
    Method setExemptions = vmRuntimeClass.getDeclaredMethod(
            "setHiddenApiExemptions", String[].class);
    setExemptions.invoke(vmRuntime, (Object) new String[]{"L"});
  }

  private static void tryDisableApiChecksLinking() {
    VMRuntime.getRuntime().setHiddenApiExemptions(new String[]{"L"});
  }

}