3.17

所花时间：2小时

代码量：47

博客篇：1

了解到的知识点

EditText的焦点监听，输入错误时焦点返回该输入框

package com.example.test1;

import android.content.Intent;
import android.os.Bundle;
import android.text.TextUtils;
import android.util.Log;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;

import androidx.activity.EdgeToEdge;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.graphics.Insets;
import androidx.core.view.ViewCompat;
import androidx.core.view.WindowInsetsCompat;

public class MainActivity extends AppCompatActivity implements View.OnClickListener, View.OnFocusChangeListener {

    private static final String TGA="aaa";
    private EditText ed_id;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ed_id = findViewById(R.id.ex_id);
        EditText ed_password = findViewById(R.id.ex_password);
        ed_password.setOnFocusChangeListener(this);
    }

    @Override
    public void onClick(View v) {
        startActivity(new Intent(this, MainActivity2.class));
    }

    @Override
    public void onFocusChange(View v, boolean hasFocus) {
        if(hasFocus){
            String id = ed_id.getText().toString();
            if(TextUtils.isEmpty(id) || id.length()<11){
                ed_id.requestFocus();
                Toast toast = Toast.makeText(MainActivity.this,"请输入11位手机号",Toast.LENGTH_SHORT);
                toast.show();
            }
        }
    }
}

　　就是不知道为什么Toast不能显示