如何根据条件选择启动Activity

Question

我有 4 个单选按钮，如下所示，我只想选择任何 4 个选项中的 1 个，并且在该用户无法返回更改他填写的选项之后有一次......当应用程序打开用户应该被引导到他选择的活动。我该怎么做？ 谢谢。

RadioButton FourthGrade = (RadioButton) findViewById(R.id.grade_4th);


            FourthGrade.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    Intent intent = new Intent(CourseSelectionActivity.this, Home.class);
                    startActivity(intent);
                }
            });

Answer 1

您可以创建一个“导航器”Activity 作为应用程序的入口点，如下所示：

public class NavigatorActivity extends AppCompatActivity {

    public static final String KEY_CHOICE = "choice";

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // fetch the choice of the user, or return -1 if there is no choice yet
        SharedPreferences prefs = PreferenceManager
                .getDefaultSharedPreferences(this);
        int choice = prefs.getInt(KEY_CHOICE, -1);
        Intent intent = createIntentBasedOnChoice(this, choice);

        startActivity(intent);
        finish();
    }

    // this method returns an Intent based on the passed choice parameter
    public static Intent createIntentBasedOnChoice(Context context, int choice) {
        Intent intent;

        switch (choice) {
            case 1: {
                intent = new Intent(context, FirstActivity.class);
                break;
            }
            case 2: {
                intent = new Intent(context, SecondActivity.class);
                break;
            }
            case 3: {
                intent = new Intent(context, ThirdActivity.class);
                break;
            }
            case 4: {
                intent = new Intent(context, FourthActivity.class);
                break;
            }
            default: {
                // if there is no choice yet, start the ChoiceActivity
                intent = new Intent(context, ChoiceActivity.class);
                break;
            }
        }
        return intent;
    }
}

这将根据用户之前的选择导航到四个活动之一。如果用户还没有选择，它将导航到ChoiceActivity。

ChoiceActivity 的基本布局：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <RadioGroup
        android:id="@+id/group_choices"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content">

        <RadioButton
            android:id="@+id/button_choice1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:checked="true"
            android:text="Choice 1" />

        <RadioButton
            android:id="@+id/button_choice2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Choice 2" />

        <RadioButton
            android:id="@+id/button_choice3"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Choice 3" />

        <RadioButton
            android:id="@+id/button_choice4"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Choice 4" />

    </RadioGroup>

    <Button
        android:id="@+id/button_submit"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="This is my choice!" />
</LinearLayout>

它的代码看起来像这样：

public class ChoiceActivity extends AppCompatActivity {

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_choice);

        final RadioGroup choiceGroup = (RadioGroup) findViewById(
            R.id.group_choices);
        Button submitButton = (Button) findViewById(R.id.button_submit);

        submitButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                int choice;

                switch (choiceGroup.getCheckedRadioButtonId()) {
                    case R.id.button_choice1: {
                        choice = 1;
                        break;
                    }
                    case R.id.button_choice2: {
                        choice = 2;
                        break;
                    }
                    case R.id.button_choice3: {
                        choice = 3;
                        break;
                    }
                    case R.id.button_choice4: {
                        choice = 4;
                        break;
                    }
                    default: {
                        choice = 1;
                        break;
                    }
                }

                // saving the choice of the user
                PreferenceManager
                    .getDefaultSharedPreferences(ChoiceActivity.this)
                    .edit()
                    .putInt(NavigatorActivity.KEY_CHOICE, choice)
                    .apply();

                Intent intent = NavigatorActivity
                    .createIntentBasedOnChoice(ChoiceActivity.this, choice);

                startActivity(intent);
                finish();
            }
        });
    }
}

这会将用户的选择保存在SharedPreferences 中并向前导航到相应的Activity。

这只是一个非常基本的示例，可以帮助您开始，根据您的需要进行调整。