你可以试试这个:

@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
    if (keyCode == KeyEvent.KEYCODE_BACK && event.getRepeatCount() == 0) {

        finish();
        return true;
    }
    return super.onKeyDown(keyCode, event);
}

只需调用这些方法来完成当前活动或通过onBackPressed返回

finish();

OR

onBackPressed();

 @Override
 public boolean onOptionsItemSelected(MenuItem item) {
      int id = item.getItemId();

      if ( id == android.R.id.home ) {
          finish();
          return true;
      }

      return super.onOptionsItemSelected(item);
 }

尝试一下，它既可以在工具栏返回按钮作为硬件返回按钮。

通过单击返回按钮从一个活动返回到另一个活动，使用下面给出的代码，使用当前活动名称，然后使用目标活动。

@Override
public void onBackPressed() {
    // do something on back.
    startActivity(new Intent(secondActivity.this, MainActivity.class));
    return;
}

默认情况下，所有新的活动/意图都有back/previous行为，除非你已经在调用活动上编写了finish()。

Android活动存储在活动堆栈中。回到以前的活动可能意味着两件事。

You opened the new activity from another activity with startActivityForResult. In that case you can just call the finishActivity() function from your code and it'll take you back to the previous activity. Keep track of the activity stack. Whenever you start a new activity with an intent you can specify an intent flag like FLAG_ACTIVITY_REORDER_TO_FRONT or FLAG_ACTIVITY_PREVIOUS_IS_TOP. You can use this to shuffle between the activities in your application. Haven't used them much though. Have a look at the flags here: http://developer.android.com/reference/android/content/Intent.html

正如注释中提到的，如果活动是用startActivity()打开的，那么可以用finish()关闭它。 如果你想使用向上按钮，你可以在onOptionsSelected(MenuItem item)方法中捕捉到，检查android.R.id.home的项目ID，而不是评论中提到的R.id.home。