[英]Keep object on screen rotation?
我知道這里已經討論過很多次了,但是我仍然沒有找到解決方案。 我正在使用ViewPager為Android創建“向導”組件,其中包含一些片段(多少片段取決於將使用此擴展程序的開發人員),並且我需要保存向導狀態。 我發現的唯一方法是強制開發人員在使用此擴展時聲明靜態片段,但我真的不喜歡這樣做(因為開發人員的操作更復雜,並且我想使其盡可能易於使用)。
我的延伸課程:
public class WizardActivity extends AppCompatActivity {
private WizardAdapter wizardAdapter;
private WizardPager wizardPager;
private Button buttonNext;
private Button buttonPrevious;
private int wizardPagerID;
private int buttonNextID;
private int buttonPreviousID;
private int layoutID;
private boolean swipeEnabled;
public WizardActivity(int layoutID, int buttonNext, int buttonPrevious, int wizardPager, boolean swipeEnabled) {
super();
this.wizardAdapter = new WizardAdapter(getSupportFragmentManager());
this.wizardPagerID = wizardPager;
this.buttonNextID = buttonNext;
this.buttonPreviousID = buttonPrevious;
this.layoutID = layoutID;
this.swipeEnabled = swipeEnabled;
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(layoutID);
wizardPager = (WizardPager) findViewById(wizardPagerID);
buttonNext = (Button) findViewById(buttonNextID);
buttonPrevious = (Button) findViewById(buttonPreviousID);
wizardPager.setAdapter(wizardAdapter);
wizardPager.setSwipeEnabled(swipeEnabled);
buttonNext.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (onNextButton(wizardPager.getCurrentItem())) {
wizardPager.showNext();
refreshButtons();
}
}
});
buttonPrevious.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if(onPreviousButton(wizardPager.getCurrentItem())) {
wizardPager.showPrevious();
refreshButtons();
}
}
});
if(savedInstanceState != null) {
wizardPager.setCurrentItem(savedInstanceState.getInt("page", 0));
}
refreshButtons();
}
@Override
public void onBackPressed() {
if (wizardPager.getCurrentItem() == 0) {
super.onBackPressed();
} else {
wizardPager.showPrevious();
refreshButtons();
}
}
@Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putInt("page", wizardPager.getCurrentItem());
}
@Override
public void onConfigurationChanged(Configuration newConfig) {
super.onConfigurationChanged(newConfig);
refreshButtons();
}
public WizardPager getWizardPager() { return wizardPager; }
public WizardAdapter getWizardAdapter() { return wizardAdapter; }
public Button getButtonNext() { return buttonNext; }
public Button getButtonPrevious() { return buttonPrevious; }
public void addWizardFragment(WizardFragment fragment) { wizardAdapter.addFragment(fragment); }
public boolean showNextFragment() {
return onNextButton(wizardPager.getCurrentItem()) && wizardPager.showNext();
}
public boolean showPreviousFragment() {
return onPreviousButton(wizardPager.getCurrentItem()) && wizardPager.showPrevious();
}
public void refreshButtons() {
WizardFragment currentFragment = wizardAdapter.getItem(wizardPager.getCurrentItem());
buttonPrevious.setEnabled(currentFragment.isPreviousEnabled());
buttonPrevious.setText(currentFragment.getPreviousText());
buttonNext.setEnabled(currentFragment.isNextEnabled());
buttonNext.setText(currentFragment.getNextText());
}
public boolean onNextButton(int currentItem) {
return true;
}
public boolean onPreviousButton(int currentItem) {
return true;
}
}
其他開發人員的類如下所示:
public class SetupActivity extends WizardActivity {
private static SetupFragment setupFragment = new SetupFragment();
private static SetupLicenseFragment setupLicenseFragment = new SetupLicenseFragment();
private static SetupLoginFragment setupLoginFragment = new SetupLoginFragment();
public SetupActivity() {
super(R.layout.activity_setup, R.id.button2, R.id.button3, R.id.pager, false);
}
@Override
protected void onCreate(Bundle savedInstanceState) {
String previousText = getString(R.string.setup_button_previous);
String nextText = getString(R.string.setup_button_next);
String finishText = getString(R.string.setup_button_finish);
setupFragment.setupFragment(previousText, nextText, false, true);
setupLicenseFragment.setupFragment(previousText, nextText, true, false);
setupLoginFragment.setupFragment(previousText, finishText, true, false);
addWizardFragment(setupFragment);
addWizardFragment(setupLicenseFragment);
addWizardFragment(setupLoginFragment);
super.onCreate(savedInstanceState);
}
@Override
public boolean onNextButton(int currentItem) {
if(currentItem == 2) {
Intent intent = new Intent(SetupActivity.this, MainActivity.class);
startActivity(intent);
finish();
return false;
}
return super.onNextButton(currentItem);
}
}
(WizardAdapter包含WizardFragments的ArrayList)
有沒有一種方法可以保存其他開發人員添加的片段,而又不會增加開發人員的難度呢?
在活動類中使片段成為靜態字段是一個壞主意,android將在配置更改期間重新創建片段,因此您的靜態實例將被銷毀。 對於未保留的片段來說確實如此,但是保留的片段主要用於保留數據而不是用於構建UI。
我建議您使用getFragmentManager().findFragmentByTag
在WizardActivity.OnCreate
重新創建向導管理器。 標簽應在初始addWizardFragment( ... );
期間存儲addWizardFragment( ... );
來自基本活動的調用-您可以輕松地從片段實例中傳遞它們。 當然,應按照處理運行時更改中所述的常規過程保存所有其他狀態。
您的客戶端不應在配置更改期間調用addWizardFragment。 因此,他們應該寫:
if ( savedInstanceState == null ) {
addWizardFragment(setupFragment);
addWizardFragment(setupLicenseFragment);
addWizardFragment(setupLoginFragment);
}
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