安卓开发-Activity-多个Activity的开发方法。

原文链接：https://blog.csdn.net/weixin_38420342/article/details/84344496

一、切换Activity的5种方式

Intent intent = new Intent();
(1)intent.setClass(this,OtherActivity.class);
(2)intent.setClassName(this,"com.xiazdong.OtherActivity");
(3)intent.setClassName("com.xiazdong","com.xiazdong.OtherActivity");//此种方式用来激活不同应用的Activity，只需要指定第一个参数：包名 为另一个应用即可；
(4)
Component comp = new Component(this,OtherActivity.class);
intent.setComponent(comp);
(5)Intent intent = new Intent(this,OtherActivity.class);
————————————————
二、发送参数与接收参数方式
1、putExtra方式：

发送
intent.putExtra("name","xiazdong");
intent.putExtra("age",20);
接收
String name = intent.getStringExtra("name");
int age = intent.getIntExtra("age");

2、Bundle方式：

发送
Bundle bundle = new Bundle();
bundle.putString("name","xiazdong");
bundle.putInt("age",20);
intent.putExtras(bundle);

接收
Bundle bundle = intent.getExtras();
String name = bundle.getString("name");
int age = bundle.getInt("age");

编写一个程序，可在第一个Activity中输入两个整数，单击“计算”按钮后，在第二个Activity负责求和计算，并将结果返回

 <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:id="@+id/tex"
         android:layout_width="fill_parent"
         android:layout_height="wrap_content"
         android:text="请输入数值" />

     <LinearLayout
         android:layout_width="fill_parent"
         android:layout_height="wrap_content"
         android:orientation="horizontal" >

         <EditText
             android:id="@+id/edt"
             android:layout_width="0dp"
             android:layout_height="wrap_content"
             android:layout_weight="1" />

         <EditText
             android:id="@+id/edt1"
             android:layout_width="0dp"
             android:layout_height="wrap_content"
             android:layout_weight="1" />
     </LinearLayout>

     <Button
         android:id="@+id/but"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:text="计算" />

     <TextView
         android:id="@+id/tex1"
         android:layout_width="300dp"
         android:layout_height="50dp"
        />

 </LinearLayout>

activity_mian.xml 程序

 <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:id="@+id/e1"
             android:layout_width="fill_parent"
             android:layout_height="40dp"
           />

         <TextView
             android:id="@+id/e2"
             android:layout_width="fill_parent"
             android:layout_height="40dp"
             />
          <TextView
             android:id="@+id/e3"
             android:layout_width="fill_parent"
             android:layout_height="40dp"
             />
   <Button
         android:id="@+id/b1"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:text="回传" />
 </LinearLayout>

activity_other.xml

 package com.example.shiyan;

 import android.os.Bundle;
 import android.app.Activity;
 import android.content.Intent;
 import android.view.Menu;
 import android.view.View;
 import android.view.View.OnClickListener;
 import android.widget.Button;
 import android.widget.EditText;
 import android.widget.TextView;

 public class MainActivity extends Activity {
     private EditText edt;
     private EditText edt1;
     private TextView tex1;
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
         edt=(EditText)this.findViewById(R.id.edt);
        edt=(EditText)this.findViewById(R.id.edt1);
        tex1=(TextView)this.findViewById(R.id.tex1);
         Button but=(Button)this.findViewById(R.id.but);
         but.setOnClickListener(new OnClickListener()
         {
             public void onClick(View v) {
                 String number = edt.getText().toString();
                 String number1 = edt.getText().toString();
                 Intent intent = new Intent();
                 intent.setClass(MainActivity.this,OtherActivity.class);
                 intent.putExtra("shu1",number);
                 intent.putExtra("shu2",number1);
                 MainActivity.this.startActivityForResult(intent,100);
             }
         });

         }

     @Override
     protected void onActivityResult(int requestCode, int resultCode, Intent data) {
         super.onActivityResult(requestCode, resultCode, data);
         if(requestCode==100&&resultCode==200){
             String a=data.getStringExtra("sum");
             tex1.setText(a);

         }

     }

     @Override
     public boolean onCreateOptionsMenu(Menu menu) {
         // Inflate the menu; this adds items to the action bar if it is present.
         getMenuInflater().inflate(R.menu.main, menu);
         return true;
     }

 }

MainActivity

 package com.example.shiyan;

 import android.os.Bundle;
 import android.app.Activity;
 import android.content.Intent;
 import android.view.Menu;
 import android.view.View;
 import android.view.View.OnClickListener;
 import android.widget.Button;
 import android.widget.EditText;
 import android.widget.TextView;

 public class OtherActivity extends Activity {
     private TextView e1;
     private TextView e2;
     private TextView e3;
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_other);
          e1=(TextView)this.findViewById(R.id.e1);
          e2=(TextView)this.findViewById(R.id.e2);
          e3=(TextView)this.findViewById(R.id.e3);
          Intent intent=getIntent();
          String a=intent.getStringExtra("shu1");
          String b=intent.getStringExtra("shu2");
          int c=Integer.parseInt(a)+Integer.parseInt(b) ;
          String str = String.valueOf(c);
          e1.setText(a);
          e2.setText(b);
          e3.setText(str);
          Button b1=(Button)this.findViewById(R.id.b1);
             b1.setOnClickListener(new OnClickListener()
             {
                 public void onClick(View v) {
                      Intent intent=getIntent();
                      String a=intent.getStringExtra("shu1");
                      String b=intent.getStringExtra("shu2");
                      int c=Integer.parseInt(a)+Integer.parseInt(b) ;
                      String str = String.valueOf(c);
                     intent.putExtra("sum",str);
                     setResult(200,intent);
                     OtherActivity.this.finish();
                 }
             });
     }

     @Override
     public boolean onCreateOptionsMenu(Menu menu) {
         // Inflate the menu; this adds items to the action bar if it is present.
         getMenuInflater().inflate(R.menu.other, menu);
         return true;
     }

 }

OtherActivity