Examples of objects and monitor events ------- android study notes four

Examples of Component Object
make key function module calculator interface on a relationship;
To
numbers in the figures show the "Display results" position.
Define objects:

  //定义对象
    Button btn1, btn2, btn3, btn4, btn5,btn6,btn7,btn8,btn9,btn0;
    Button[] btn = new Button[10];//button类对象
    int[]  btnId = {R.id.btn0, R.id.btn1,R.id.btn2,R.id.btn3,R.id.btn4,R.id.btn5,R.id.btn6,R.id.btn7,R.id.btn8,R.id.btn9};
    TextView txtResult;

    @Override

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        this.setContentView(R.layout.calc);
        this.findViewById(R.id.btn1);
        txtResult = (TextView) this.findViewById(R.id.textResult);
        }

Here is binding instance of Component Object listening for events

//        initView();//绑定监听事件
//        myClick myClick = new myClick();
//        for(int i=0;i<btn.length;i++){
//            btn[i].setOnClickListener(myClick);
//        }

//        btn1.setOnClickListener(new myClick());
//        btn2.setOnClickListener(new myClick());
//        btn3.setOnClickListener(new myClick());
//        btn4.setOnClickListener(new myClick());
//        btn5.setOnClickListener(new myClick());
//        btn6.setOnClickListener(new myClick());
//        btn7.setOnClickListener(new myClick());
//        btn8.setOnClickListener(new myClick());
//        btn9.setOnClickListener(new myClick());
//        btn0.setOnClickListener(new myClick());

//    void initView(){//实例化组建对象
//        txtResult = (TextView) this.findViewById(R.id.textResult);
//        for(int i = 0;i<btn.length;i++){
//            btn[i] =(Button) this.findViewById(btnId[i]);
//        }
//    }
        /*
        btn1 = (Button) this.findViewById(R.id.btn1);//实例化组建对象
        btn2 = (Button) this.findViewById(R.id.btn2);
        btn3 = (Button) this.findViewById(R.id.btn3);
        btn4 = (Button) this.findViewById(R.id.btn4);
        btn5 = (Button) this.findViewById(R.id.btn5);
        btn6 = (Button) this.findViewById(R.id.btn6);//实例化组建对象
        btn7 = (Button) this.findViewById(R.id.btn7);
        btn8 = (Button) this.findViewById(R.id.btn8);
        btn9 = (Button) this.findViewById(R.id.btn9);
        btn0 = (Button) this.findViewById(R.id.btn0);*/

The above two are the code of violence to solve problems; here it will make the code optimization:

public class MainActivity extends AppCompatActivity {

    TextView tv;
    //alt+enter自动导入包
    //定义对象
    Button btn1, btn2, btn3, btn4, btn5,btn6,btn7,btn8,btn9,btn0;
    Button[] btn = new Button[10];
    int[]  btnId = {R.id.btn0, R.id.btn1,R.id.btn2,R.id.btn3,R.id.btn4,R.id.btn5,R.id.btn6,R.id.btn7,R.id.btn8,R.id.btn9};
    TextView txtResult;

    @Override

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        this.setContentView(R.layout.calc);
        this.findViewById(R.id.btn1);
        txtResult = (TextView) this.findViewById(R.id.textResult);
    }
     //定义一个单击方法检测并返回按键的值
    public void myOnclick(View  v){
        switch (v.getId()) {
            case R.id.btn1://通过传来的Id进行检测并返回这个按钮的值
                txtResult.setText("1");//在显示结果的地方返回值  1  
                break;
            case R.id.btn2:
                txtResult.setText("2");
                break;
            case R.id.btn3:
                txtResult.setText("3");
                break;
            case R.id.btn4:
                txtResult.setText("4");
                break;
            case R.id.btn5:
                txtResult.setText("5");
                break;
            case R.id.btn6:
                txtResult.setText("6");
                break;
            case R.id.btn7:
                txtResult.setText("7");
                break;
            case R.id.btn8:
                txtResult.setText("8");
                break;
            case R.id.btn9:
                txtResult.setText("9");
                break;
            case R.id.btn0:
                txtResult.setText("0");
                break;
        }
    }
}

The code above are implemented in MainActivity.java in
a good, relevant content is to achieve these objects and events in the monitor.
Some additional knowledge:
listener definition:
the listener is actually a class that implements a particular interface, then this class is described in the web.xml file so that the server at startup can instantiate the class , start the listener. When the range of the state of the object changes, the server automatically listener object method invocation.
Definition of the interface:
the interface definition keyword: interface
defined format:

public interface 接口名  extends 接口,...  {
   //定义常量
   public static final 数据类型  常量名 = 值;
   
   //定义抽象方法
   public abstract 返回值数据类型  方法名(数据类型 参数名,...);
  }

Listener methods:

btn1.setOnClickListener(new myClick());