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[操作系统]Activity详解三 启动activity并返回结果

首先看演示:

1 简介

、如果想在Activity中得到新打开Activity 关闭后返回的数据,需要使用系统提供的startActivityForResult(Intent intent, int requestCode)方法打开新的Activity,新的Activity 关闭后会向前面的Activity传回数据,为了得到传回的数据,必须在前面的Activity中重写onActivityResult(int requestCode, int resultCode, Intent data)方法。

public class MainActivity extends Activity {  private final static String TAG="MainActivity";  @Override  public void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.main);        Button btnOpen=(Button)this.findViewById(R.id.btnOpen);    btnOpen.setOnClickListener(new View.OnClickListener(){      public void onClick(View v) {        //得到新打开Activity关闭后返回的数据        //第二个参数为请求码,可以根据业务需求自己编号        startActivityForResult(new Intent(MainActivity.this, OtherActivity.class), 1);      }    });  }  /**   * 为了得到传回的数据,必须在前面的Activity中(指MainActivity类)重写onActivityResult方法   *   * requestCode 请求码,即调用startActivityForResult()传递过去的值   * resultCode 结果码,结果码用于标识返回数据来自哪个新Activity   */  @Override  protected void onActivityResult(int requestCode, int resultCode, Intent data) {    String result = data.getExtras().getString("result");//得到新Activity 关闭后返回的数据    Log.i(TAG, result);  }}

  

当新Activity关闭后,新Activity返回的数据通过Intent进行传递,android平台会调用前面Activity 的onActivityResult()方法,把存放了返回数据的Intent作为第三个输入参数传入,在onActivityResult()方法中使用第三个输入参数可以取出新Activity返回的数据。

                    

2 setResult

使用startActivityForResult(Intent intent, int requestCode)方法打开新的Activity,新Activity关闭前需要向前面的Activity返回数据需要使用系统提供的setResult(int resultCode, Intent data)方法实现:

public class OtherActivity extends Activity {   @Override  protected void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.other);     Button btnClose=(Button)findViewById(R.id.btnClose);    btnClose.setOnClickListener(new View.OnClickListener(){      public void onClick(View v) {        //数据是使用Intent返回        Intent intent = new Intent();        //把返回数据存入Intent        intent.putExtra("result", "My name is linjiqin");        //设置返回数据        OtherActivity.this.setResult(RESULT_OK, intent);        //关闭Activity        OtherActivity.this.finish();      }    });      } }setResult()方法的第一个参数值可以根据业务需要自己定义,上面代码中使用到的RESULT_OK是系统Activity类定义的一个常量,值为-1,代码片断如下:public class android.app.Activity extends ......{ public static final int RESULT_CANCELED = 0; public static final int RESULT_OK = -1; public static final int RESULT_FIRST_USER = 1;}

 

说明:当点击“打开新的Activity”按钮,会跳转到“我是新打开的Activity”页面;

        当点击“关闭”按钮,关闭当前页面,同时跳转到“我是旧的Activity”页面,且会传递result参数给前一个Activity

3请求码的作用                

使用startActivityForResult(Intent intent, int requestCode)方法打开新的Activity,我们需要为startActivityForResult()方法传入一个请求码(第二个参数)。请求码的值是根据业务需要由自已设定,用于标识请求来源。例如:一个Activity有两个按钮,点击这两个按钮都会打开同一个Activity,不管是那个按钮打开新Activity,当这个新Activity关闭后,系统都会调用前面Activity的onActivityResult(int requestCode, int resultCode, Intent data)方法。在onActivityResult()方法如果需要知道新Activity是由那个按钮打开的,并且要做出相应的业务处理,这时可以这样做:

 

@Override public void onCreate(Bundle savedInstanceState) {    ....    button1.setOnClickListener(new View.OnClickListener(){      public void onClick(View v) {        startActivityForResult (new Intent(MainActivity.this, NewActivity.class), 1);      }    });    button2.setOnClickListener(new View.OnClickListener(){      public void onClick(View v) {         startActivityForResult (new Intent(MainActivity.this, NewActivity.class), 2);      }    });                 @Override protected void onActivityResult(int requestCode, int resultCode, Intent data) {        switch(requestCode){          case 1:          //来自按钮1的请求,作相应业务处理          case 2:          //来自按钮2的请求,作相应业务处理        }     }}

  

4 结果码的作用

在一个Activity中,可能会使用startActivityForResult()方法打开多个不同的Activity处理不同的业务,当这些新Activity关闭后,系统都会调用前面Activity的onActivityResult(int requestCode, int resultCode, Intent data)方法。为了知道返回的数据来自于哪个新Activity,在onActivityResult()方法中可以这样做(ResultActivity和NewActivity为要打开的新Activity):

public class ResultActivity extends Activity {    .....    ResultActivity.this.setResult(1, intent);    ResultActivity.this.finish();}public class NewActivity extends Activity {    ......    NewActivity.this.setResult(2, intent);    NewActivity.this.finish();}public class MainActivity extends Activity { // 在该Activity会打开ResultActivity和NewActivity    @Override protected void onActivityResult(int requestCode, int resultCode, Intent data) {        switch(resultCode){          case 1:          // ResultActivity的返回数据          case 2:          // NewActivity的返回数据        }     }} 

5 Demo源码:

TestResultActivity.java

package mm.shandong.com.testresult;import android.content.Intent;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.view.View;import android.widget.EditText;import android.widget.RadioButton;import android.widget.RadioGroup;import android.widget.TextView;public class TestResultActivity extends AppCompatActivity {  EditText editTextBrand;  RadioGroup radioGroup;  TextView textViewXH;  @Override  protected void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.activity_test_result);    editTextBrand = (EditText) findViewById(R.id.editTextBrand);    radioGroup = (RadioGroup) findViewById(R.id.radioGroup);    textViewXH = (TextView) findViewById(R.id.textViewXH);    RadioButton radionButton = (RadioButton) radioGroup.getChildAt(0);    radionButton.setChecked(true);  }  ///跳转到选择品牌界面  public void selectBrand(View view) {    Intent intent = new Intent(this, TestResultActivity1.class);    startActivityForResult(intent, 1);  }  ///选择要购买的电脑  public void selectCompute(View view) {    Intent intent = new Intent(this, TestResultActivity2.class);    String brand = editTextBrand.getText().toString();    RadioButton radionButton =        (RadioButton) radioGroup.findViewById(radioGroup.getCheckedRadioButtonId());    String nc = radionButton.getText().toString();    intent.putExtra("brand", brand);    intent.putExtra("nc", nc);    startActivityForResult(intent, 2);    textViewXH.setText("");  }  ///activity请求返回的回调  @Override  protected void onActivityResult(int requestCode, int resultCode, Intent intent) {    switch (requestCode) { //resultCode为回传的标记      case 1:        if (resultCode == 2) {          String brand = intent.getStringExtra("brand");          editTextBrand.setText(brand);        }        break;      case 2:        if (resultCode == 3) {          String xh = intent.getStringExtra("xh");          textViewXH.setText(xh);        }        break;    }  }}

TestResultActivity1

package mm.shandong.com.testresult;import android.content.Intent;import android.os.Bundle;import android.support.v7.app.AppCompatActivity;import android.view.View;import android.widget.ArrayAdapter;import android.widget.ListView;import android.widget.Toast;public class TestResultActivity1 extends AppCompatActivity {  ListView listView;  String[] brands = new String[]{"联想", "戴尔"};  @Override  protected void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.activity_test_result1);    listView = (ListView) findViewById(R.id.listView);    ArrayAdapter arrayAdapter = new ArrayAdapter(this,          android.R.layout.simple_list_item_checked, brands);    listView.setAdapter(arrayAdapter);    listView.setChoiceMode(ListView.CHOICE_MODE_SINGLE);  }  ///提交选择的品牌结果  public void submit(View view) {    int index = listView.getCheckedItemPosition();    if (index < 0) {      Toast.makeText(this, "请选择品牌", Toast.LENGTH_SHORT).show();      return;    }    String brand = (String) listView.getItemAtPosition(index);    int resultCode = 2;    Intent intent = getIntent();    intent.putExtra("brand", brand);    setResult(2, intent);    finish();  }}

 

 

TestResultActivity2

package mm.shandong.com.testresult;import android.content.Intent;import android.os.Bundle;import android.support.v7.app.AppCompatActivity;import android.view.View;import android.widget.ArrayAdapter;import android.widget.ListView;import android.widget.Toast;import java.util.ArrayList;import java.util.HashMap;import java.util.List;import java.util.Map;public class TestResultActivity2 extends AppCompatActivity {  ListView listView;  @Override  protected void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.activity_test_result2);    Intent intent=getIntent();    String brand=intent.getStringExtra("brand");    String nc=intent.getStringExtra("nc");    Map map=initData();    List<String> lists= (List<String>) map.get(brand+nc);    listView= (ListView) findViewById(R.id.listView);    ArrayAdapter arrayAdapter=new ArrayAdapter(this,               android.R.layout.simple_list_item_checked,lists);    listView.setAdapter(arrayAdapter);    listView.setChoiceMode(ListView.CHOICE_MODE_SINGLE);  }  ///提交选择的电脑型号  public void submit(View view){    int index= listView.getCheckedItemPosition();    if(index<0){      Toast.makeText(this,"请选择型号",Toast.LENGTH_SHORT).show();      return ;    }    String xh= (String) listView.getItemAtPosition(index);    int resultCode=2;    Intent intent=getIntent();    intent.putExtra("xh",xh);    setResult(3,intent);    finish();  }  ///初始化数据源  public Map initData(){    Map map=new HashMap();    List<String> lists=new ArrayList<>();    lists.add("联想1G0001");    lists.add("联想1G0002");    map.put("联想1G",lists);    lists=new ArrayList<>();    lists.add("联想2G0001");    lists.add("联想2G0002");    map.put("联想2G",lists);    lists=new ArrayList<>();    lists.add("戴尔1G0001");    lists.add("戴尔1G0002");    map.put("戴尔1G",lists);    lists=new ArrayList<>();    lists.add("戴尔2G0001");    lists.add("戴尔2G0002");    map.put("戴尔2G",lists);    return map;  }}

 


 

 

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最后,以上例子都来源与安卓无忧,请去应用宝或者豌豆荚下载:http://android.myapp.com/myapp/detail.htm?apkName=com.shandong.mm.androidstudy,源码例子文档一网打尽