android 封装事件监听

基本的事件监听方式

package com.example.myapplication;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;
import androidx.appcompat.app.AppCompatActivity;
public class LineList extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_line_list);
        Button btn1 = findViewById(R.id.button1);
        btn1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Toast.makeText(LineList.this, "helloworld", Toast.LENGTH_SHORT).show();
            }
        });
    }
}

基本的逻辑

Button btn1 = findViewById(R.id.button1);
btn1.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {
        Toast.makeText(LineList.this, "helloworld", Toast.LENGTH_SHORT).show();
    }
});

• findViewById 找到这个元素
• 调用setOnClickListener 方法，传入一个View的OnclickListener实例，并重写了onClick方法

封装 View.OnClickListener

package com.example.myapplication;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;
import androidx.appcompat.app.AppCompatActivity;
public class LineList extends AppCompatActivity {
    private Button btn1;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_line_list);
        btn1 = findViewById(R.id.button1);
        OnClick onClick = new OnClick();
        btn1.setOnClickListener(onClick);
    }
    class OnClick implements View.OnClickListener {
        @Override
        public void onClick(View v) {
            switch (v.getId()) {
                case R.id.button1:
                    Toast.makeText(LineList.this, "helloworld", Toast.LENGTH_SHORT).show();
                    break;
            }
        }
    }
}

重写好OnClickListener

class OnClick implements View.OnClickListener {
    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.button1:
                Toast.makeText(LineList.this, "helloworld", Toast.LENGTH_SHORT).show();
                break;
        }
    }
}

用setOnClickListener时直接传入这个写好的View.OnClickListener的实例

OnClick onClick = new OnClick();
btn1.setOnClickListener(onClick);