Question

我正在尝试保存我在单独的活动中动态制作的按钮，但我似乎无法让它工作。以下是我在CreateButton.java中尝试过的内容：

    private static final AtomicInteger sNextGeneratedId = new AtomicInteger(1);

public static int generateViewId() {
    for (;;) {
        final int result = sNextGeneratedId.get();
        // aapt-generated IDs have the high byte nonzero; clamp to the range under that.
        int newValue = result + 1;
        if (newValue > 0x00FFFFFF) newValue = 1; // Roll over to 1, not 0.
        if (sNextGeneratedId.compareAndSet(result, newValue)) {
            return result;
        }
    }
}

public void Submit (View view) {
        Intent myIntent = new Intent(CreateNewClass.this, MainActivity.class);
        EditText mEdit   = (EditText)findViewById(R.id.class_name);
        String name = mEdit.getText().toString();

        mEdit   = (EditText)findViewById(R.id.class_semester);
        String semester = mEdit.getText().toString();

        mEdit   = (EditText)findViewById(R.id.class_year);
        String year = mEdit.getText().toString();

        Button myButton = new Button(this);

        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.JELLY_BEAN_MR1) {
            myButton.setId(generateViewId());
        }
        else {
            myButton.setId(Button.generateViewId());
        }

        myButton.setText(name + " " + semester + " " + year);

        setContentView(R.layout.activity_main);
        LinearLayout ll = (LinearLayout)findViewById(R.id.main_screen);
        LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams
                (LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT);
        ll.addView(myButton, layoutParams);

        startActivity(myIntent);
    }

这是activity_main的我的.xml：

    <?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/main_screen"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">
    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="@string/select" />

    <Button
        android:layout_height="wrap_content"
        android:clickable="true"
        android:autoLink="web"
        android:layout_width="match_parent"
        android:id="@+id/button_so"
        android:text="@string/Google"
        android:linksClickable="true"
        android:onClick="goToGoogle"/>


    <Button
        android:layout_height="wrap_content"
        android:layout_width="match_parent"
        android:text="@string/newClass"
        android:autoLink="web"
        android:clickable="true"
        android:id="@+id/button_su"
        android:onClick="goToCreate"/>
</LinearLayout>

它在mainActivity上动态创建按钮并导航到它，但我无法保存按钮，它会立即返回到两个原始按钮。

任何帮助都非常感谢，我是一个新手，我只是想学习一些这方面的东西。谢谢！

Answer 1

这是因为您首先使用setContentView设置了视图，这基本上只显示您在当前活动中充气的布局。然后你开始一个新的Activity，它自己启动一个完全独立的View，因此仍然显示默认按钮。

如果要设置文本并在实际的Activity中添加Button，最好将String作为Intent Extra传递。

因此，您的submit方法应如下所示：

//by the way you shouldn't start method names with upper case
public void submit (View view) {
        Intent myIntent = new Intent(CreateNewClass.this, MainActivity.class);
        EditText mEdit   = (EditText)findViewById(R.id.class_name);
        String name = mEdit.getText().toString();

        mEdit   = (EditText)findViewById(R.id.class_semester);
        String semester = mEdit.getText().toString();

        mEdit   = (EditText)findViewById(R.id.class_year);
        String year = mEdit.getText().toString();

        String buttonText = name + " " + semester + " " + year;

        myIntent.putExtra("button_text", buttonText);

        startActivity(myIntent);
    }

然后在MainActivity中，您可以通过将以下代码粘贴到onCreate方法中来放置按钮。

Intent intent = getIntent();
String buttonText = intent.getStringExtra("button_text");

//activity could also be started without providing the extra
if(buttonText != null){
    Button button = new Button(this);
    button.setText(buttonText);
    LinearLayout ll = (LinearLayout)findViewById(R.id.main_screen);
    LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams
      (LinearLayout.LayoutParams.WRAP_CONTENT, 
      LinearLayout.LayoutParams.WRAP_CONTENT);
    ll.addView(button, layoutParams);
}

修改

好的，既然你想要实现一些与我想的不同的东西，你应该尝试另一种方法。

您正尝试从第二个活动中获得Result，因此最好在此处使用startActivityForResult()（请参阅documentation）方法。我假设您的应用程序使用MainActivity作为第一个显示的Activity。

不是通过发出startActivity()来启动第二个活动，而是使用startActivityForResult()提供任何常量作为请求代码。在submit方法中，您可以移除startActivity(myIntent)行，而是将以下代码放在那里：

setResult(Activity.RESULT_OK, myIntent); finish();

再次在MainActivity中，您可以使用以下实现覆盖onActivityResult方法：

@Override protected void onActivityResult(int requestCode, int resultCode, Intent data) { //you specified the request code before, when launching the second activity if(requestCode == ADD_USER_REQUEST){ if(resultCode == Activity.RESULT_OK){ String buttonText = data.getStringExtra("button_text"); if(buttonText != null){ Button button = new Button(this); button.setText(buttonText); LinearLayout ll = (LinearLayout)findViewById(R.id.main_screen); LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams (LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT); ll.addView(button, layoutParams); //here comes the part that saves the button strings persistently SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(getApplicationContext()); Set<String> buttonSet = prefs.getStringSet("saved_buttons",null); if(buttonSet == null){ buttonSet = new HashSet<String>(); } buttonSet.add(buttonText); prefs.edit.putStringSet("saved_buttons", buttonSet).commit(); } } }

最后，当活动重新启动时，您需要重建旧布局。将以下代码放在MainActivity.onCreate中，删除Intent Extra内容。

SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(getApplicationContext()); Set<String> buttonSet = prefs.getStringSet("saved_buttons", null); if(buttonSet != null){ LinearLayout ll = (LinearLayout)findViewById(R.id.main_screen); for(String buttonText : buttonSet){ Button button = new Button(this); button.setText(buttonText); LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams (LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT); ll.addView(button, layoutParams); } }

保存动态创建的按钮android

1 个答案: