2010年6月13日 星期日

Android程式設計(十二) Activity互動作業-2

處理Activity間資料傳遞
要傳遞資料給被啟動的Activity,啟用端Activity必須先使用putExtra()方法以name-value pair方式設定所要傳遞的資料。putExtra()方法第1個參數代表資料名稱,第2個參數則是為資料內容,如需要傳遞多筆資料,只要重複使用putExtra()方法即可。例如:
Intent intent = new Intent (MainActivity.this, Activity1.class);
intent.putExtra ("REQ1", "MainActivity傳遞的資料1");
intent.putExtra ("REQ2", "MainActivity傳遞來的資料2");
startActivity (intent);
被啟動的Activity,必須先使用getIntent()方法取得傳來的「Intent」物件,再透過getExtras()方法取得資料包(bundle),然後使用getString()等方法讀取指定資料。例如:
Bundle params = getIntent().getExtras();
if (params! = null) {
    temp = params.getString ("REQ1") + "\n" + params.getString ("REQ2");
    Toast.makeText (Activity1.this, temp, Toast.LENGTH_LONG).show();
}
如果啟用端想要由被啟動的Activity取得回傳資料,那麼啟用端必須改用startActivityForResult()方法來啟動Activity,並覆寫onActivityResult()方法來處理被啟動之Activity所回傳的資料。
startActivityForResult()方法的第二個參數為自訂的請求碼,主要是做為雙方溝通的標記,這個請求碼會在onActivityResult()方法中的第一個參數被傳回,以便onActivityResult()程式驗證回傳者身份。
//MainActivity.java
public class MainActivity extends Activity {
    final int MY_ID = 100;
    @Override
    public void onCreate (Bundle savedInstanceState) {
        Button btnobj;
        super.onCreate (savedInstanceState);
        setContentView (R.layout.main);
        btnobj = (Button) findViewById (R.id.btnINVOKE02);
        btnobj.setOnClickListener (InvokeActivity2);
    }
    private Button.OnClickListener InvokeActivity2 = new Button.OnClickListener () {
        public void onClick (View v) {
            Intent intent = new Intent (MainActivity.this, Activity2.class);
            intent.putExtra ("REQ1", "MainActivity傳遞的資料1");
            intent.putExtra ("REQ2", "MainActivity傳遞的資料2");
            startActivityForResult (intobj, MY_ID);
        }
    };
    @Override
    protected void onActivityResult (int requestCode, int resultCode, Intent data) {
        super.onActivityResult (requestCode, resultCode, data);
        if (requestCode == MY_ID){
            String temp = null;
            Bundle results = data.getExtras ();
            if (results != null){
                temp = results.getString ("ACK1") + results.getString ("ACK2");
                Toast.makeText (MainActivity.this, temp, Toast.LENGTH_LONG).show();
            }
        }
    }
}
被啟動的Activity端所要回傳的資料亦是使用putExtra ()方法設定name-value pair,之後再使用setResult ()方法回傳資料。
//Activity2.java
public class Activity2 extends Activity {
    final int ACK = 200;
    @Override
    protected void onCreate (Bundle savedInstanceState) {
        Button btnobj;
        super.onCreate (savedInstanceState);
        setContentView (R.layout.activity2);
        btnobj = (Button) findViewById (R.id.btnRETURN);
        btnobj.setOnClickListener (CloseActivity2);
        String temp = null;
        Bundle params = getIntent().getExtras();
        if (params! = null){
            temp = params.getString ("REQ1") + "\n" + params.getString ("REQ2");
            Toast.makeText (Activity2.this, temp, Toast.LENGTH_LONG).show();
        }
    }
    private Button.OnClickListener CloseActivity2 = new Button.OnClickListener() {
        public void onClick (View v) {
            Intent intent = new Intent ();
            intent.putExtra ("ACK1", "Activity2傳回的資料1");
            intent.putExtra ("ACK2", "Activity2傳回的資料2");
            setResult (ACK, intent);
            finish ();
        }
    };
}

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