Android-----Intent通过startActivityForResult(Intent intent , int 标志符)启动新的Activity

我们都了解使用 startActivity(intent) 新的activity只能传递数据，却无法返回数据，返回新activity返回的数据我们可以替换startActivityForResult(Intent intent , int 标志符)

做个备忘录的例子，两个activity： IntentDemo 和  IntentSecend：

activity_intent_demo.xml代码如下：

 <LinearLayout
     xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     android:orientation="vertical"
     tools:context="com.hs.example.exampleapplication.IntentDemo">

     <ListView
         android:id="@+id/intent_listView"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"/>

 </LinearLayout>

IntentDemo 代码如下：

 public class IntentDemo extends AppCompatActivity implements AdapterView.OnItemClickListener ,
         AdapterView.OnItemLongClickListener{

     String [] aMemo = {"1.单击可以编辑备忘" , "2.长按可以清楚备忘" , "3." , "4." , "5." , "6."};

     ArrayAdapter<String> arrayAdapter;

     ListView intent_listView ;

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

         intent_listView  = this.findViewById(R.id.intent_listView);

         arrayAdapter = new ArrayAdapter<>(this,android.R.layout.simple_list_item_1,aMemo);

         intent_listView.setAdapter(arrayAdapter);           //设置list view的内容
         intent_listView.setOnItemClickListener(this);       //绑定单击监听
         intent_listView.setOnItemLongClickListener(this);   //绑定长按监听
     }

     @Override
     public void onItemClick(AdapterView<?> adapterView, View view, int pos, long l) {
         Intent intent = new Intent(this,IntentSecend.class);
         //intent.putExtra("编号",pos + 1);       //传递编号
         intent.putExtra("备忘",aMemo[pos]);            //传递备忘内容
         startActivityForResult(intent , pos); //跳转到编辑内容activity,并以选项位置pos为标志符
     }

     @Override
     public boolean onItemLongClick(AdapterView<?> adapterView, View view, int i, long l) {
         aMemo[i] = (i+1) + ".";                             //清楚内容，只剩编号
         arrayAdapter.notifyDataSetChanged();                //通知list view更新要显示的内容
         return true;
     }

     @Override
     protected void onActivityResult(int requestCode , int resultCode , Intent intent){
         if(resultCode == RESULT_OK){
             aMemo[requestCode] = intent.getStringExtra("备忘");
             Toast.makeText(this,aMemo[requestCode].toString(),Toast.LENGTH_SHORT).show();
             arrayAdapter.notifyDataSetChanged();
         }
     }
 }

activity_intent_secend.xml代码如下：

 <?xml version="1.0" encoding="utf-8"?>
 <LinearLayout
     xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     android:orientation="vertical"
     tools:context="com.hs.example.exampleapplication.IntentSecend">

     <TextView
         android:id="@+id/text_view"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:background="#FBBB"
         android:gravity="top"
         android:text="1."
         />

     <EditText
         android:id="@+id/edit_Text"
         android:layout_width="match_parent"
         android:layout_height="0dp"
         android:layout_weight="1"
         android:gravity="top"/>

     <LinearLayout
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
         android:gravity="center"
         android:orientation="horizontal">

         <Button
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
             android:onClick="onCancel"
             android:text="取消"/>

         <Button
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
             android:onClick="onSave"
             android:text="保存"/>

     </LinearLayout>

 </LinearLayout>

IntentSecend代码如下：

 public class IntentSecend extends AppCompatActivity {

     TextView tv ;
     EditText et ;

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

         Intent intent = getIntent();

         String str = intent.getStringExtra("备忘");             //读取传过来的备注数据

         tv = this.findViewById(R.id.text_view);
         tv.setText(str.substring(0,2));                             //text view的值

         et = this.findViewById(R.id.edit_Text);
         if(str.length()>2){                                             //将传过来的数据去除前两个字符，然后填入edittext
             et.setText(str.substring(2));
         }
     }

     public void onSave(View view) {
         Intent intent2 = new Intent();
         intent2.putExtra("备忘",tv.getText() + "" + et.getText());
         setResult(RESULT_OK , intent2);
         finish();
     }

     public void onCancel(View view) {
         setResult(RESULT_CANCELED);
         finish();
     }

 }

运行效果：