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：