Launching activity through intents

问题:

I am implementing a simple app. I need to start an activity based on the state of the Activity. Lets take i am using a button to start the activity. 1. If the activity is not started, I need to start XYZ activity. 2. If the XYZ activity is on focus, then i need to close the activity on the button press. 3. If the XYZ activity is not in focus (like onPause) state then, I need to change the button state.

Can you please help me in the flags that i need to use for starting the intent. Is it possible to get the state of activity before I start that activity?

回答1:

Try this

Intent intent = new Intent(currentActivity.this, callingActivity.class); startActivity(intent);

You can use intent like this to call an activity

回答2:

The button press will need to be captured by each activity separately, so just code the different responses into each different activity.

回答3:

First off create a MAIN.java activity that is going to house your other activities. Like others have said you're going to have to code the button captures yourself because that should be common sense if you're trying to deal with intents. When you get that together though, you can start a new activity through intent like so:

// allocate new intent, initialized to the activity you wish to launch
Intent i = new Intent(this, ActivityToBeLaunched.class);

// put information into intent
i.putExtras("KeyName", value); // where "KeyName" is simply a reference string
                         // and 'value' can be anything from boolean - string.

// launch activity and wait for response
startActivityForResult(i, REQUEST_CODE);

Then within your ActivityToBeLaunched.java class you'll have an oncreate that will pull information from the intent like such:

// get intent
Intent i = this.getIntent();

// get information from intent
booleanVariable = i.getExtras().getBoolean("KeyName");

When you're done with this activity simply use;

   // create intent
   Intent i = new Intent();

   // put information into result to send back to parent
   i.putExtras("KeyName", value);

   // set the result to be returned
   setResult(i, ResultCode);

    // finish child, return to parent with results
    finish();