android 自定义alertdialog和取消dialog

看代码：

public class MainActivity extends AppCompatActivity {

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

        findViewById(R.id.btn).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);
                LayoutInflater inflater = getLayoutInflater();
                View view1 = inflater.inflate(R.layout.alert, (ViewGroup) findViewById(R.id.alertdialog));
                builder.setView(view1);
                final AlertDialog dialog = builder.show();
                view1.findViewById(R.id.btn_invent).setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View view) {
                        Log.e("tag", "onClick: "+"点击取消" );
                        dialog.dismiss();
                    }
                });

            }
        });
    }
}

要取消dialog先要获取dialog，再dismiss（），直接dismiss（）是没有用的；
demo下载地址：https://github.com/renjiemei1225/AlertDialogTest2