我已经完全重写了这个问题,以便缩小范围.
我有两个片段像卡片一样翻转(左,右).当前片段消失翻转时,它会显示背面.再次单击该按钮后,它会再次翻转到前面,但前面片段上的ImageView消失了.
我尝试过保存所选图像数据的不同方法.
>保存碎片onSaveInstanceState
这给了我一个空指针,所以我想我创建后需要一些更恒定的东西.
>所以现在我将图像保存到SDCard一次
这个我认为可行,只需检查路径并抓住它,如果它翻转到前面或重新创建活动.
这是一些代码
的onCreate()：
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.new_postcard_activity);
//UI call
frontImageView = (ImageView) findViewById(R.id.imageView);
Log.d(tag,"onCreate() Instance:" + savedInstanceState);
//fragment start
if (savedInstanceState == null) {
Log.d(tag,"Instance Null");
getFragmentManager()
.beginTransaction()
.add(R.id.postcardFrame,new CardFrontFragment())
.commit();
if(!mShowingBack){
Log.d(tag,"Not showing back");
if(newPath != null && newPath != ""){
Log.d(tag,"entered new path,not empty");
Drawable drawable = Drawable.createFromPath(newPath);
Log.d(tag,"Should be setting saved image.");
frontImageView.setImageDrawable(drawable);
}
}
}
else
{
mShowingBack = (getFragmentManager().getBackStackEntryCount() > 0);
Log.d(tag,"Instance is not Null");
}
翻转按钮单击“侦听器”
//flip card
final Button cardBackButton = (Button) findViewById(R.id.cardBackButton);
cardBackButton.setOnClickListener(new Button.OnClickListener(){
@Override
public void onClick(View v) {
flipCard();
});
flipCard方法：
private void flipCard()
{
Log.d(tag2,"Log after flipCard:" + mShowingBack);
if(mShowingBack)
{
//Flip to front
flipFront();
return;
}
// Flip to back
flipBack();
}
我从他们的PhotoGallery中设置了Image onActivityResult
protected void onActivityResult(int requestCode,int resultCode,Intent intent) {
super.onActivityResult(requestCode,resultCode,intent);
if (resultCode == RESULT_OK) {
Uri photoUri = intent.getData();
if (photoUri != null) {
try {
ImageView setImage = (ImageView)findViewById(R.id.imageView);
frontImage = MediaStore.Images.Media.getBitmap(this
.getContentResolver(),photoUri);
imageSet = true;
//save image to SD
if(imageSet == true){
Log.d(tag,"Inside Image Set if Statement");
String path = getExternalCacheDir() + "Postcards.png";
if(path != null && path != ""){
Log.d(tag,"Path is:" + path);
File file = new File(path);
newPath = file.getAbsolutePath();
Log.d(tag,"New Path:" + newPath);
if(file.exists()){
Log.d(tag,"File Exists");
Drawable d = Drawable.createFromPath(newPath);
setImage.setImageDrawable(d);
}else{
try{
Log.d(tag,"File didnt exist");
FileOutputStream out = new FileOutputStream(file);
frontImage.compress(Bitmap.CompressFormat.PNG,90,out);
if(file.exists()){
Log.d(tag,"file exists now");
newPath = file.getAbsolutePath();
Drawable b = Drawable.createFromPath(newPath);
setImage.setImageDrawable(b);
}
}catch(Exception e){
e.printStackTrace();
}
}
}
}
} catch (Exception e) {
e.printStackTrace();
}
这是我访问图像并尝试在Restart()上将其设置为我的ImageView的方式
if(imageSet == true){
if(newPath != null && newPath != ""){
ImageView view = (ImageView) findViewById(R.id.imageView);
Drawable drawable = Drawable.createFromPath(newPath);
view.setImageDrawable(drawable);
}
}
这似乎是获取图像和设置图像的最佳途径,但它不会工作.
什么是最佳实践,如何让它以我需要的方式执行？
非常感谢任何帮助！
解决方法
savedInstanceState用于不同的目的.
onSaveInstanceState (Bundle):
This method is called before an activity may be killed so that when it
comes back some time in the future it can restore its state
而且,在您的特定情况下,甚至可能不需要它.单击按钮,您将更改片段,而不是重新启动应用程序.
从我所看到的,你让用户创建一张明信片：一面是图片(比如A面),另一面是消息(比如说B面).当应用程序启动时,A侧即可查看.在某种程度上,您让用户从图库中选择一个图像.我将假设onActivityResult(int,int,Intent)按预期工作,并将图像设置为ImageView – R.id.imageView.单击按钮时,视图将更改为B侧.再次单击该按钮时,视图将更改为A面,但用户选择的图像不存在.
你可以在onActivityResult(int,Intent)中做的一件事是：在SharedPreferences中保存图像的路径.
SharedPreferences preferences;
final String PREFS = "your.application.name.prefs";
// Keyword to find the path
final String IMAGE_SELECTED_BY_USER = "image_selected_by_user";
// Use a default image when the user starts the app for the first time
// or if the retrieved path points to a deleted image etc.
final String PATH_TO_A_DEFAULT_IMAGE = "path_to_a_default_image"
@Override
protected void onCreate(Bundle savedInstanceState) {
....
....
preferences = getActivity().getSharedPreferences(PREFS,0);
imagePath = preferences.getString(IMAGE_SELECTED_BY_USER,PATH_TO_A_DEFAULT_IMAGE);
frontImageView = (ImageView) findViewById(R.id.imageView);
Drawable drawable = null;
if (new File(imagePath).exists()) {
drawable = Drawable.createFromPath(imagePath);
} else {
drawable = Drawable.createFromPath(PATH_TO_A_DEFAULT_IMAGE);
}
frontImageView.setImageDrawable(drawable);
getFragmentManager()
.beginTransaction()
.add(R.id.postcardFrame,new CardFrontFragment())
.commit();
....
....
}
在onActivityResult(int,Intent)中,保存图像路径：
if(file.exists()){
Log.d(tag,"File Exists");
Drawable d = Drawable.createFromPath(newPath);
setImage.setImageDrawable(d);
Editor editor = preferences.edit();
editor.putString(IMAGE_SELECTED_BY_USER,newPath);
editor.commit();
} else{
try{
Log.d(tag,"File didnt exist");
FileOutputStream out = new FileOutputStream(file);
frontImage.compress(Bitmap.CompressFormat.PNG,out);
if (file.exists()) {
Log.d(tag,"file exists now");
newPath = file.getAbsolutePath();
Drawable b = Drawable.createFromPath(newPath);
setImage.setImageDrawable(b);
Editor editor = preferences.edit();
editor.putString(IMAGE_SELECTED_BY_USER,newPath);
editor.commit();
}
} catch (Exception e) {
e.printStackTrace();
}
}
这样,当用户启动应用程序时,他/她将看到默认图像或先前选择的图像.
其中savedInstanceState很有用：假设你给用户一个在B面写短信的选项.现在,如果在写消息时,用户将设备从Landscape旋转到Portrait(反之亦然),那么消息他就是/她写的将会消失,因为活动将被销毁并重新创建.要保存消息,可以使用onSaveInstanceState(Bundle)：
@Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putString("Text_To_Save",someEditText.getText().toString());
}
轮换时,将调用活动的onCreate(Bundle)’.传递的包与fromSaveInstanceState(Bundle)`相同.要检索文本：
String savedString = "";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (savedInstanceState != null) {
if (savedInstanceState.contains("Text_To_Save")) {
savedString = savedInstanceState.getString("Text_To_Save");
}
}
someEditText.setText(savedString);
}
