要开始一项活动，您需要使用意图。您可以在单击按钮时调用它，如下所示：
Button myButton = (Button) findViewById(R.id.MY_BUTTON);
myButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(CurrentActivity.class, NextActivity.class);
startActivity(intent);
}
为了让它变得随机，我们需要稍微改变一下，让它更像这样：
Button myButton = (Button) findViewById(R.id.MY_BUTTON);
myButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// Here, we are generating a random number
Random generator = new Random();
int number = generator.nextInt(5) + 1;
// The '5' is the number of activities
Class activity = null;
// Here, we are checking to see what the output of the random was
switch(number) {
case 1:
// E.g., if the output is 1, the activity we will open is ActivityOne.class
activity = ActivityOne.class;
break;
case 2:
activity = ActivityTwo.class;
break;
case 3:
activity = ActivityThree.class;
break;
case 4:
activity = ActivityFour.class;
break;
default:
activity = ActivityFive.class;
break;
}
// We use intents to start activities
Intent intent = new Intent(getBaseContext(), activity);
startActivity(intent);
}
}
如果您愿意，可以阅读更多关于启动活动和使用意图的信息here。
更新问题/评论的更新答案：
如果你不想打开已经打开的 Activity，那会稍微复杂一些。
在您的主要活动中添加以下代码（与上一个答案中的代码几乎相同，但略有不同）：
Button myButton = (Button) findViewById(R.id.MY_BUTTON);
myButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// We are creating a list, which will store the activities that haven't been opened yet
ArrayList<Class> activityList = new ArrayList<>();
activityList.add(ActivityOne.class);
activityList.add(ActivityTwo.class);
activityList.add(ActivityThree.class);
activityList.add(ActivityFour.class);
activityList.add(ActivityFive.class);
Random generator = new Random();
int number = generator.nextInt(5) + 1;
Class activity = null;
// Here, we are checking to see what the output of the random was
switch(number) {
case 1:
activity = ActivityOne.class;
// We are adding the number of the activity to the list
activityList.remove(ActivityOne.class);
break;
case 2:
activity = ActivityTwo.class;
activityList.remove(ActivityTwo.class);
break;
case 3:
activity = ActivityThree.class;
activityList.remove(ActivityThree.class);
break;
case 4:
activity = ActivityFour.class;
activityList.remove(ActivityFour.class);
break;
default:
activity = ActivityFive.class;
activityList.remove(ActivityFive.class);
break;
}
// We use intents to start activities
Intent intent = new Intent(getBaseContext(), activity);
// `intent.putExtra(...)` is used to pass on extra information to the next activity
intent.putExtra("ACTIVITY_LIST", activityList);
startActivity(intent);
}
}
在所有其他 5 个活动中，使用以下代码：
Button myButton = (Button) findViewById(R.id.ANOTHER_BUTTON);
myButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
ArrayList<Class> activityList = new ArrayList<>();
Bundle extras = getBaseContext().getIntent().getExtras();
activityList = extras.get("ACTIVITY_LIST");
if(activityList.size() == 0) {
// Do something when after all activities have been opened
doSomeAction();
} else {
// Now, the random number is generated between 1 and however many
// activities we have remaining
Random generator = new Random();
int number = generator.nextInt(activityList.size()) + 1;
Class activity = null;
// Here, we are checking to see what the output of the random was
switch(number) {
case 1:
// We will open the first remaining activity of the list
activity = activityList.get(0);
// We will now remove that activity from the list
activityList.remove(0);
break;
case 2:
// We will open the second remaining activity of the list
activity = activityList.get(1);
activityList.remove(1);
break;
case 3:
// We will open the third remaining activity of the list
activity = activityList.get(2);
activityList.remove(2);
break;
case 4:
// We will open the fourth remaining activity of the list
activity = activityList.get(3);
activityList.remove(3);
break;
default:
// We will open the fifth remaining activity of the list
activity = activityList.get(4);
activityList.remove(4);
break;
}
// Note: in the above, we might not have 3 remaining activities, for example,
// but it doesn't matter because that case wouldn't be called anyway,
// as we have already decided that the number would be between 1 and the number of
// activities left.
// Starting the activity, and passing on the remaining number of activities
// to the next one that is opened
Intent intent = new Intent(getBaseContext(), activity);
intent.putExtra("ACTIVITY_LIST", activityList);
startActivity(intent);
}
}
}
编辑：[07/07/2020]
这篇文章是很久以前写的，我忽略了很多东西。
Tenfour04 是正确的，我们需要 switch 语句，因此可以更简洁：
int r = new Random().nextInt(activityList.size);
Class<? extends Activity> activity = activityList.removeAt(r);