我尝试将字符串从一个活动传递到另一个活动。 这是活动A ：
中的编码@Override
public void onSaveInstanceState(Bundle savedInstanceState) {
savedInstanceState.putString("UserName", UserName);
Log.i(Tag, "UserName1: "+ UserName);
super.onSaveInstanceState(savedInstanceState);
}
在活动B 中，我使用此代码获取字符串：
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.add_item);
setUpViews();
if (savedInstanceState != null){
UserName = savedInstanceState.getString("UserName");
}
Log.i(Tag, "UserName2: "+ UserName);
}
但当我将活动B 打开时，logcat显示第一个日志“UserName1”， 并将第二个日志“UserName2”显示为“null”。
我可能知道我的代码有什么问题吗？
我想要做的是当我点击“按钮”并意图活动B时，活动A传递活动B中的字符串。所以我可以在活动B中获得字符串值。
任何想法？因为我在使用intent.putStringExtra（）和getintent.getStringExtra（）时遇到错误，所以我改为使用onSaveInstanceState（），但仍然有问题。
修改 这是我的原始代码，我可以在活动B 中获取字符串，但意外的是我无法在Sqlite中保存我的数据。如果删除了putString Extra，那么一切都会顺利进行。
@Override
public boolean onOptionsItemSelected(MenuItem item) {
Intent addItem = new Intent(ItemActivity.this, AddEditItem.class).setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
addItem.putStringExtra("UserName", UserName);
Log.e(Tag, "UseName: "+ UserName);
startActivity(addItem);
return super.onOptionsItemSelected(item);
}
活动B中的代码：
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.add_item);
setUpViews();
UserName = (String) getIntent().getStringExtra("UserName");
Log.e(Tag, "UserName3: "+ UserName);
}
活动B的完整代码：
public class AddEditItem extends Activity implements OnItemSelectedListener {
private static final String Tag = null;
private EditText inputItemName;
private EditText inputItemCondition;
private EditText inputEmail;
private Button btnGal, btnConfirm;
private Bitmap bmp;
private ImageView ivGalImg;
private Spinner spinner;
String[] category = {"Books", "Clothes & Shoes", "Computer", "Electronics", "Entertainment", "Food & Drinks",
"Furnitures", "Mobile Phone", "Other", "UKM"};
String selection;
String filePath, itemName, itemCondition;
String UserName, user;
private int id;
private byte[] blob=null;
byte[] byteImage2 = null;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.add_item);
setUpViews();
if (savedInstanceState != null){
UserName = savedInstanceState.getString("UserName");
}
Log.e(Tag, "UserName2: "+ UserName);
//UserName = (String) getIntent().getStringExtra("UserName");
//Log.e(Tag, "UserName3: "+ UserName);
}
private void setUpViews() {
inputItemName = (EditText)findViewById(R.id.etItemName);
inputItemCondition = (EditText)findViewById(R.id.etItemCondition);
inputEmail = (EditText)findViewById(R.id.etEmail);
ivGalImg = (ImageView) findViewById(R.id.ivImage);
ArrayAdapter<String> adapter = new ArrayAdapter<String>(AddEditItem.this, android.R.layout.simple_spinner_dropdown_item, category);
spinner = (Spinner)findViewById(R.id.spnCategory);
spinner.setAdapter(adapter);
spinner.setOnItemSelectedListener(this);
Bundle extras = getIntent().getExtras();
if (extras != null) {
id=extras.getInt("id");
user=extras.getString("user");
inputItemName.setText(extras.getString("name"));
inputItemCondition.setText(extras.getString("condition"));
inputEmail.setText(extras.getString("email"));
selection = extras.getString("category");
byteImage2 = extras.getByteArray("blob");
if (byteImage2 != null) {
if (byteImage2.length > 3) {
ivGalImg.setImageBitmap(BitmapFactory.decodeByteArray(byteImage2,0,byteImage2.length));
}
}
}
btnGal = (Button) findViewById(R.id.bGallary);
btnGal.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
intent.setType("image/*");
startActivityForResult(intent, 0);
}
});
btnConfirm = (Button) findViewById(R.id.bConfirm);
btnConfirm.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (inputItemName.getText().length() != 0 && inputItemCondition.getText().length() != 0
&& inputEmail.getText().length() != 0) {
AsyncTask<Object, Object, Object> saveItemTask = new AsyncTask<Object, Object, Object>() {
@Override
protected Object doInBackground(Object... params) {
saveItem();
return null;
}
@Override
protected void onPostExecute(Object result) {
Toast.makeText(getApplicationContext(),
"Item saved", Toast.LENGTH_LONG)
.show();
finish();
}
};
saveItemTask.execute((Object[]) null);
Toast.makeText(getApplicationContext(),
"Item saved reconfirm", Toast.LENGTH_LONG)
.show();
} else {
AlertDialog.Builder alert = new AlertDialog.Builder(
AddEditItem.this);
alert.setTitle("Error In Save Item");
alert.setMessage("You need to fill in all the item details");
alert.setPositiveButton("OK", null);
alert.show();
}
}
});
}
private void saveItem() {
if(bmp!=null){
ByteArrayOutputStream outStr = new ByteArrayOutputStream();
bmp.compress(CompressFormat.JPEG, 100, outStr);
blob = outStr.toByteArray();
}
else{blob=byteImage2;}
ItemSQLiteConnector sqlCon = new ItemSQLiteConnector(this);
if (getIntent().getExtras() == null) {
sqlCon.insertItem(UserName, inputItemName.getText().toString(),
inputItemCondition.getText().toString(),
inputEmail.getText().toString(),
selection, blob);
}
else {
sqlCon.updateItem(id, UserName, inputItemName.getText().toString(),
inputItemCondition.getText().toString(),
inputEmail.getText().toString(),
selection, blob);
}
}
@Override
protected void onActivityResult(int requestCode, int resultCode,Intent resultdata) {
super.onActivityResult(requestCode, resultCode, resultdata);
switch (requestCode) {
case 0:
if (resultCode == RESULT_OK) {
Uri selectedImage = resultdata.getData();
String[] filePathColumn = { MediaStore.Images.Media.DATA };
Cursor cursor = getContentResolver().query(selectedImage,
filePathColumn, null, null, null);
cursor.moveToFirst();
int columnIndex = cursor.getColumnIndex(filePathColumn[0]);
String filePath = cursor.getString(columnIndex);
cursor.close();
// Convert file path into bitmap image using below line.
bmp = BitmapFactory.decodeFile(filePath);
ivGalImg.setImageBitmap(bmp);
}
}
}
@Override
public void onItemSelected(AdapterView<?> parent, View view,
int pos, long id) {
// TODO Auto-generated method stub
TextView tv = (TextView)view;
selection = tv.getText().toString();
}
@Override
public void onNothingSelected(AdapterView<?> arg0) {
// TODO Auto-generated method stub
}
}
答案 0 :(得分：0)
我可能知道我的代码有什么问题吗？
onSaveInstanceState()与在活动之间传递数据无关。相反，您需要在与Intent一起使用的startActivity()上添加额外的字符串。
因为我在使用intent.putExtra（）和getintent.getExtra（）时遇到错误
由于这是正确的方法（虽然使用getStringExtra()），请回到它并修正您遇到的任何错误。
答案 1 :(得分：0)
onSaveInstanceState不用于此目的，它用于保存您的活动状态，例如方向更改，或者当您离开活动并返回它时。 你需要的是使用意图。
除了启动活动之外，意图还可以在整个应用程序中携带一些信息，如下所示： 这将是活动1：
Intent = new Intent (getApplicationContext(), Activity2.class);
intent.putExtra("UserName", UserName);
startActivity(intent);
并在第二次活动中恢复它：
String username = getIntent().getExtras().getString("UserName");