四大组件_Activity_2.通过显示意图启动Activity

如果一个Application只有一个Activity的话，Application能创造的价值可就比现在少很多了。我们需要Activity之间能够灵活的跳转，除了跳转，它能够在不同的Activity之间传送数据才算意思。
今天我们来写一个活动跳转的demo(账户登录)，并了解一下显式意图启动Activity

• 展示结果（不会上传动态图）
  
  

• 显式启动Activity

• 当前Activity

Intent intent = new Intent(MainActivity.this,SecondActivity.class);//参数：当前上下文、要跳转活动的字节码文件
                intent.putExtra("account",accountText);//数据传输
                intent.putExtra("password",passwordText);
                startActivity(intent);//启动Activity

• 跳转Activity方

		Intent intent = getIntent();//响应
        account = intent.getStringExtra("account");//接收数据
        password = intent.getStringExtra("password");

• 来具体看看这个demo
  • xml布局文件(activity_main)

<?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:orientation="vertical"
    tools:context=".MainActivity">

    <TextView
        android:layout_marginTop="20dp"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="账号"/>
    <EditText
        android:id="@+id/account_edit"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="密码"/>
    <EditText
        android:id="@+id/password_edit"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:inputType="textPassword"/>
    <Button
        android:id="@+id/sign_in_button"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="立即登录"/>

</LinearLayout>

• activity_second.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:orientation="vertical"
    tools:context=".SecondActivity">
    <TextView
        android:id="@+id/account_text"
        android:layout_marginTop="20dp"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="您的账户是：******"/>
    <TextView
        android:id="@+id/password_text"
        android:layout_marginTop="10dp"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="您的密码是：******"/>
</LinearLayout>

• MainActivity

package com.example.firstactivity;

import androidx.appcompat.app.AppCompatActivity;

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

public class MainActivity extends AppCompatActivity {

    private EditText mAccount;
    private EditText mPassword;
    private Button mLogin;
    private String TAG = "MainActivity";
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initView();//初始化UI
        initListener();//初始化监听
    }

    private void initListener() {
        mLogin.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Log.d(TAG,"登录被点击");
                handleLogin();
            }

            private void handleLogin() {
                String accountText = mAccount.getText().toString().trim();
                String passwordText = mPassword.getText().toString().trim();
                if (TextUtils.isEmpty(accountText)) {//判断账户是否为空
                    Toast.makeText(MainActivity.this,"账号为空",Toast.LENGTH_SHORT).show();
                    return;
                }
                if (TextUtils.isEmpty(passwordText)) {//判断密码是否为空
                    Toast.makeText(MainActivity.this,"密码为空",Toast.LENGTH_SHORT).show();
                    return;
                }

                Intent intent = new Intent(MainActivity.this,SecondActivity.class);
                intent.putExtra("account",accountText);
                intent.putExtra("password",passwordText);
                startActivity(intent);
            }
        });
    }

    private void initView() {
        mAccount = findViewById(R.id.account_edit);
        mPassword = findViewById(R.id.password_edit);
        mLogin = findViewById(R.id.sign_in_button);
    }
}

• SecondActivity

package com.example.firstactivity;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.widget.TextView;

public class SecondActivity extends AppCompatActivity {

    private TextView mAccount;
    private TextView mPassword;
    private String account;
    private String password;
    String TAG = "SecondActivity";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_second);
        initData();////初始化数据
    }

    private void initData() {
        Intent intent = getIntent();
        account = intent.getStringExtra("account");
        password = intent.getStringExtra("password");
        Log.e(TAG,"account:"+account);
        Log.e(TAG,"password:"+password);
        initView();//初始化UI
    }

    private void initView() {
        mAccount = findViewById(R.id.account_text);
        mPassword = findViewById(R.id.password_text);
        mAccount.setText("您的账号是："+account+"\n");
        mPassword.setText("您的密码是："+password+"\n");
    }
}

• 新手提示：不要忘记在AndroidManifest中注册新建的Activity

本文地址：https://blog.csdn.net/weixin_44618862/article/details/107561595