键盘事件OnKeyListener

1.效果图：就是在文本框中输入A，则显示A，输入B，则显示B....

(1)activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.app3.MainActivity"
    android:orientation="vertical">

    <EditText
        android:id="@+id/et"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />
    <TextView
        android:id="@+id/tv_show"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="" />
</LinearLayout>

 (2)MainAcivity.java

package com.example.app3;

import android.content.DialogInterface;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {
    private EditText editText;
    private TextView textView;

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

        editText = (EditText) findViewById(R.id.et);
        textView = (TextView) findViewById(R.id.tv_show);

        editText.setOnKeyListener(new View.OnKeyListener() {
            @Override
            public boolean onKey(View v, int keyCode, KeyEvent event) {         //注意这里参数的变化
                switch (event.getKeyCode()){
                    case KeyEvent.KEYCODE_A:
                        textView.setText("点击了A");
                        break;
                    case KeyEvent.KEYCODE_B:
                        textView.setText("点击了B");
                        break;
                    case KeyEvent.KEYCODE_C:
                        textView.setText("点击了C");
                        break;
                }
                return false;
            }
        });

    }
}

 2.效果图：实现输入银行卡号，输入一个数，显示一个数，直到输出所有的银行卡号，四位显示一个空格

（1）activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.app3.MainActivity"
    android:orientation="vertical">

    <EditText
        android:id="@+id/et"
        android:hint="请输入您的银行卡号"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />
    <TextView
        android:id="@+id/tv_show"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="" />
</LinearLayout>

 (2)MainAcivity.java

package com.example.app3;

import android.content.DialogInterface;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {
    private EditText editText;
    private TextView textView;

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

        editText = (EditText) findViewById(R.id.et);
        textView = (TextView) findViewById(R.id.tv_show);

        editText.setOnKeyListener(new View.OnKeyListener() {
            @Override
            public boolean onKey(View v, int keyCode, KeyEvent event) {
            editText.setOnKeyListener(new View.OnKeyListener() {
                @Override
                public boolean onKey(View v, int keyCode, KeyEvent event) {
                    switch (event.getAction()){
                        case KeyEvent.ACTION_UP:
                            String info = editText.getText().toString();
                            textView.setText("您输入的银行卡号是："+subs(info));
                        case  KeyEvent.ACTION_DOWN:
                            break;
                    }
                    return false;
                }
            });
                return false;
            }
        });

    }

    public String subs(String info){
        String mess="";
        for(int i =0;i<=info.length()/4;i++){
            if(i*4+4<info.length()){
                mess=mess+info.substring(i*4,i*4+4)+"  ";
            }else{
                mess=mess+info.substring(i*4,info.length());
            }
        }
        return mess;
    }
}