public class MainActivity extends AppCompatActivity {
    private static final String TAG = "MainActivity";
    private Context mContext;
    ArrayList<String> titleArrayList;
    private RecyclerView mRecyclerView;
    AdView mAdView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        MobileAds.initialize(this, new OnInitializationCompleteListener() {
            @Override
            public void onInitializationComplete(InitializationStatus initializationStatus) {
            }
        });
        mAdView = findViewById(R.id.adView);
        AdRequest adRequest = new AdRequest.Builder().build();
        mAdView.loadAd(adRequest);
        mAdView.setAdListener(new AdListener() {
            @Override
            public void onAdLoaded() {
                // 当广告加载完成时执行的代码。
            }
            @Override
            public void onAdFailedToLoad(int errorCode) {
                // 当广告请求失败时执行的代码。
            }
            @Override
            public void onAdOpened() {
                // 当广告打开覆盖屏幕时执行的代码。
            }
            @Override
            public void onAdClicked() {
                // 当用户点击广告时执行的代码。
            }
            @Override
            public void onAdLeftApplication() {
                // 当用户离开应用程序时执行的代码。
            }
            @Override
            public void onAdClosed() {
                // 当用户在点击广告后返回应用程序时执行的代码。
            }
        });
        mContext = MainActivity.this;
        titleArrayList = new ArrayList<String>();
        titleArrayList.add(Constants.Title_1);
        titleArrayList.add(Constants.Title_2);
        titleArrayList.add(Constants.Title_3);
        titleArrayList.add(Constants.Title_4);
        titleArrayList.add(Constants.Title_5);
        mRecyclerView = (RecyclerView) findViewById(R.id.title_layout_RecyclerView);
        mRecyclerView.setHasFixedSize(true);
        mRecyclerView.setLayoutManager(new LinearLayoutManager(getApplicationContext()));
        TitleAdapter adapter = new TitleAdapter(mContext, titleArrayList, new CustomItemClickListener() {
            @Override
            public void onItemClick(View v, int position) {
                Intent desIntent = new Intent(mContext, DescriptionActivity.class);
                desIntent.putExtra("titles", titleArrayList.get(position));
                startActivity(desIntent);
                Toast.makeText(mContext, "clicked" + titleArrayList.get(position), Toast.LENGTH_SHORT).show();
            }
        });
        mRecyclerView.setAdapter(adapter);
    }
}