Android 中的监听和按键处理详情

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <TextView
        android:id="@+id/textView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="#F08080"
        android:padding="10dp"
        android:text="触屏监听" />

    <Button
        android:id="@+id/button"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:elevation="1dp"
        android:text="长按监听" />

    <Spinner
        android:id="@+id/spinner"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="#EED2EE"
        android:padding="20dp" />

    <ListView
        android:id="@+id/listview"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="#D1EEEE" />
</LinearLayout>

public class MainActivity extends AppCompatActivity {
    private TextView textview;
    private Button button;
    private Spinner spinner;
    private ListView listview;
    private String[] cities;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        setData();//准备要在列表中要显示的数据
        setViews();//获得控件，并在列表中显示数据
        setListeners();//为控件设置监听器
    }

    private void setData() {
        cities = new String[]{"北京", "天津", "河北",
                "黑龙江", "吉林", "辽宁", "内蒙古",
                "新疆", "西藏", "江苏", "上海"
        };
    }

    private void setViews() {
        textview = findViewById(R.id.textView);
        button = findViewById(R.id.button);
        spinner = findViewById(R.id.spinner);
        listview = findViewById(R.id.listview);

        //列表和下拉菜单显示城市列表
        //一段神秘的代码...
        ArrayAdapter<String> adapter = null;
        adapter = new ArrayAdapter<>(this, android.R.layout.simple_list_item_1, cities);
        listview.setAdapter(adapter);

        adapter = new ArrayAdapter<>(this, android.R.layout.simple_spinner_item, cities);
        adapter.setDropDownViewResource(android.R.layout.simple_expandable_list_item_1);
        spinner.setAdapter(adapter);
    }

    private void setListeners() {
        textview.setOnTouchListener((view, motionEvent) -> {
            switch (motionEvent.getAction()) {
                //按下
                case MotionEvent.ACTION_DOWN:
                    Toast.makeText(MainActivity.this, "按下", Toast.LENGTH_SHORT).show();
                    break;
                //抬起
                case MotionEvent.ACTION_UP:
                    Toast.makeText(MainActivity.this, "抬起", Toast.LENGTH_SHORT).show();
                    break;
                //移动
                case MotionEvent.ACTION_MOVE:
                    //Toast.makeText(MainActivity.this, "移动", Toast.LENGTH_SHORT).show();
                    break;
            }
            return true;
        });

        button.setOnLongClickListener(view -> {
            Toast.makeText(MainActivity.this, "长按了按钮", Toast.LENGTH_SHORT).show();
            //返回布尔值true
            return true;
        });


        spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
            @Override
            public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
                Toast.makeText(MainActivity.this, "下标" + i + "城市" + cities[i], Toast.LENGTH_SHORT).show();
            }

            @Override
            public void onNothingSelected(AdapterView<?> adapterView) {
            }
        });

        listview.setOnItemClickListener((adapterView, view, i, l) -> Toast.makeText(MainActivity.this, "下标" + i + "城市" + cities[i], Toast.LENGTH_SHORT).show());
    }
}

@Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        //日志
        Log.d("ONKEYDOWN", "keyCode:" + keyCode);
        //判断其按下的是否为返回键（Back）
        if (keyCode == KeyEvent.KEYCODE_BACK) {
            Toast.makeText(this, "连按2下退出应用程序", Toast.LENGTH_SHORT).show();
        }
        //按照默认方式处理
        return super.onKeyDown(keyCode, event);
    }

ONKEYDOWN: keyCode:4

public class MainActivity extends AppCompatActivity {
    private long lastBackDownTime;

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

    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        //日志
        Log.d("ONKEYDOWN", "keyCode:" + keyCode);
        //判断其按下的是否为返回键（Back）
        if (keyCode == KeyEvent.KEYCODE_BACK) {
            //获取当前按下Back键的时间
            long currentBackDownTime = System.currentTimeMillis();
            //与上一次按下Back键的时间对比
            //如果时间差不超过1000ms，判定为连续按下，则退出
            //否则再次提示
            if (currentBackDownTime - lastBackDownTime < 1000) {
                finish();
            } else {
                Toast.makeText(this, "连按2下退出应用程序", Toast.LENGTH_SHORT).show();
                //如果没有退出，则记录本次按下Back键时间，作为下次时间参考
                lastBackDownTime = currentBackDownTime;
            }

            return true;
        }
        //按照默认方式处理
        return super.onKeyDown(keyCode, event);
    }
}

@Override
    public void onBackPressed() {
        long currentBackDownTime = System.currentTimeMillis();
        if (currentBackDownTime - lastBackDownTime < 1000) {
            finish();
        } else {
            Toast.makeText(this, "连按2下退出应用程序", Toast.LENGTH_SHORT).show();
            lastBackDownTime = currentBackDownTime;
        }
        super.onBackPressed();
    }

@Override
public void onBackPressed() {
	if(currentTag.equals("xx")) {
		doSomething();
    } else {
        // handle by activity
        super.onBackPressed();
	}
}