android Button默认点击一次

具体使用方法：

btn.performClick();

 例子：

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button btn = findViewById(R.id.btn1);
        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Toast.makeText(MainActivity.this, "点击按钮了", Toast.LENGTH_SHORT).show();
            }
        });
        btn.performClick();//就这一行代码
    }
}