Question

我正在尝试创建活动，这些活动会指向主页并打开主页屏幕，“数据库现在已更新”。但是，我不知道如何在收到意图时抽出吐司。但我不知道如何很好地接受意图，这是我的代码。

public class MainActivity extends Activity {

TextView time;
Button viewStock, descriptionSearch;
String lastUpdateStandard = "Last Update Time: ";

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

    viewStock = (Button) findViewById(R.id.detailSearchButton);
    descriptionSearch = (Button) findViewById(R.id.descriptionSearchButton);
    time = (TextView) findViewById(R.id.time);

    // retrieve time from database to see last update time
    DatabaseHandler db = new DatabaseHandler(getApplicationContext());
    List<String> lastUpdateTime = db.getLastUpdate();
    time.setText(lastUpdateStandard + lastUpdateTime.get(0));

    Intent receivedIntent = getIntent();
    /**
     *
     * What should I write if there is no received Intent? 
     * Probably I need an if-else statement, but I have no idea how it should be made. 
     */
}

Answer 1

由于所有活动都是由意图启动的（Android是按照这种方式设计的），因此建议不要进行当前想要进行的检查，它们将始终返回意图。您应该做的是检查用于启动活动的意图是否具有您要提取的数据。你显然只是因为你需要某种意图正确的数据而需要这个意图吗？因此，不应检查是否返回了意图，而应检查您从意图中获得的额外内容。例如，如果你想用字符串＆＃34; hello＆＃34;来提取额外的内容。作为关键，你将使用：

Intent receivedIntent = getIntent();
if(receivedIntent.getStringExtra("hello") != null) {
    // Means the intent has the data you expect
} else {
    // It does not have the data you expect
    // Do some processing here
}

如果您要检查是否收到意图，您将始终获得一个值

Android：Intent收到if - else

1 个答案: