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[英]How to pass edittext values from recyclerview adapter to activity in android
[英]How to Pass Values from Adapter to Activity
我試圖顯示項目列表以及GrandTotal Amount,但是每當我在代碼中使用此代碼獲取NullPointerException時 ,請參見該代碼下方:
if (Constants.sItem_Detail.size() > 0) {
Double mGTotal = Double.parseDouble(Constants.sItem_Detail.get(0).get(com.example.sample.CartAdapter.KEY_TOTAL));
for (int i = 1; i < Constants.sItem_Detail.size(); i++) {
mGTotal = mGTotal + Double.parseDouble(Constants.sItem_Detail.get(i).get(com.example.sample.CartAdapter.KEY_TOTAL));
}
mGrandTotal = String.valueOf(new DecimalFormat("##.#").format(mGTotal));
mTxtViewGrandTotal.setText(mGrandTotal);
myTextVeiwGrandTotal.setText(mGrandTotal);
特別是,當我使用這些行時出現錯誤:
Double mGTotal = Double.parseDouble(Constants.sItem_Detail.get(0).get(com.example.sample.CartAdapter.KEY_TOTAL));
mGTotal = mGTotal + Double.parseDouble(Constants.sItem_Detail.get(i).get(com.example.sample.CartAdapter.KEY_TOTAL));
我試過下面的代碼:
if (Constants.sItem_Detail.size() > 0) {
Toast.makeText(getApplicationContext(), "Constants is Greater Than 0", Toast.LENGTH_LONG).show();
} else {
Toast.makeText(getApplicationContext(), "Constants is Less Than < 0", Toast.LENGTH_LONG).show();
}
並且獲取常量大於0,並且顯示購物車中的項目數為1,但是每當我在代碼中使用此行時出現問題,這是從適配器到活動獲取價值的正確方法嗎?
Double.parseDouble(Constants.sItem_Detail.get(0).get(com.example.sample.CartAdapter.KEY_TOTAL));
實際上,我正在計算Adapter類中每個項目的總金額,現在嘗試將所有總金額的總和顯示為Activity中的總計,但是面臨問題,請告訴我我在哪里做錯了?
這是完整的代碼:
CartActivity.java:
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_cart);
mLstView1 = (ListView) findViewById(R.id.listView1);
mTxtViewGrandTotal = (TextView) findViewById(R.id.bill_amount);
myTextVeiwGrandTotal =(TextView) findViewById(R.id.mTxtViewGrandTotalValue);
mItems = (TextView) findViewById(R.id.total_items);
mTax =(TextView) findViewById(R.id.taxes);
mDeliveryCharges =(TextView) findViewById(R.id.delivery_charges);
mDiscount =(TextView) findViewById(R.id.discount);
mPackaging =(TextView) findViewById(R.id.packaging);
if (Constants.sItem_Detail.size() > 0) {
Double mGTotal = Double.parseDouble(Constants.sItem_Detail.get(0).get(com.example.sample.CartAdapter.KEY_TOTAL));
for (int i = 1; i < Constants.sItem_Detail.size(); i++) {
mGTotal = mGTotal + Double.parseDouble(Constants.sItem_Detail.get(i).get(com.example.sample.CartAdapter.KEY_TOTAL));
}
mGrandTotal = String.valueOf(new DecimalFormat("##.#").format(mGTotal));
mTxtViewGrandTotal.setText(mGrandTotal);
myTextVeiwGrandTotal.setText(mGrandTotal);
mTaxes = String.valueOf(mTax);
mTax.setText("0");
mDelivery = String.valueOf(mDeliveryCharges);
mDeliveryCharges.setText("0");
mTotal = String.valueOf(Constants.sItem_Detail.size());
mItems.setText(mTotal);
}
mViewCartAdpt = new CartAdapter(CartActivity.this);
mLstView1.setAdapter(mViewCartAdpt);
mLstView1.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View v, final int position, long id) {
//
}
});
}
// Called when the activity begins interacting with the user
@Override
protected void onResume() {
super.onResume();
mViewCartAdpt.notifyDataSetChanged();
}
}
CartAdapter.java:
public class CartAdapter extends BaseAdapter {
public static final String LOG_TAG = "CartAdapter";
public static final String KEY_TITLE = "title";
public static final String KEY_COST = "cost";
public static final String KEY_QTY = "qty";
public static final String KEY_TOTAL = "total";
Activity activity;
LayoutInflater inflater;
ImageButton mImgBtnDelete;
ListView listView;
private double itemamount = 0;
private int itemquantity = 0;
public CartAdapter(Activity a) {
// TODO Auto-generated constructor stub
activity = a;
inflater = (LayoutInflater) activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
public int getCount() {
// TODO Auto-generated method stub
return Constants.sItem_Detail.size();
}
public Object getItem(int position) {
// TODO Auto-generated method stub
return position;
}
public long getItemId(int position) {
// TODO Auto-generated method stub
return position;
}
public View getView(final int position, View convertView, ViewGroup parent) {
// TODO Auto-generated method stub
View vi = convertView;
if (convertView == null)
vi = inflater.inflate(R.layout.listrow_cart, null); // listrow_cart
vi.setClickable(true);
vi.setFocusable(true);
vi.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v)
{
}
});
mImgBtnDelete = (ImageButton) vi
.findViewById(R.id.mImgBtnDelete);
mImgBtnDelete.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
Constants.sItem_Detail.remove(position);
notifyDataSetChanged();
Intent mInViewCartRefresh = new Intent(activity,
CartActivity.class);
activity.startActivity(mInViewCartRefresh);
activity.finish();
}
});
final TextView title = (TextView) vi.findViewById(R.id.title);
final EditText qty = (EditText) vi.findViewById(R.id.qty);
final TextView cost = (TextView) vi.findViewById(R.id.cost);
final TextView total = (TextView) vi.findViewById(R.id.total);
HashMap<String, String> item = new HashMap<String, String>();
item = Constants.sItem_Detail.get(position);
// Setting all values in listview
title.setText(item.get(com.example.sample.ItemsActivity.KEY_TITLE));
cost.setText(item.get(com.example.sample.ItemsActivity.KEY_COST));
qty.setText("1");
itemquantity = Integer.parseInt(qty.getText().toString());
itemamount = Double.parseDouble(cost.getText().toString());
total.setText(new DecimalFormat("##.#").format(itemamount*itemquantity));
qty.addTextChangedListener(new TextWatcher() {
public void onTextChanged(CharSequence s, int start, int before,
int count) {
// TODO Auto-generated method stub
if (!qty.getText().toString().equals("")
|| !qty.getText().toString().equals("")) {
// accept quantity by user
itemquantity = Integer.parseInt(qty.getText()
.toString());
// changes in total amount as per change in qty (entered by user)
total.setText(new DecimalFormat("##.#").format(itemamount*itemquantity));
} else {
total.setText("0.00");
}
}
public void beforeTextChanged(CharSequence s, int start, int count,
int after) {
// TODO Auto-generated method stub
}
public void afterTextChanged(Editable s) {
}
});
return vi;
}
}
Logcat:
07-02 05:05:29.411: D/AndroidRuntime(802): Shutting down VM
07-02 05:05:29.420: W/dalvikvm(802): threadid=1: thread exiting with uncaught exception (group=0x40a71930)
07-02 05:05:29.501: E/AndroidRuntime(802): FATAL EXCEPTION: main
07-02 05:05:29.501: E/AndroidRuntime(802): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.sample/com.example.sample.CartActivity}: java.lang.NullPointerException
07-02 05:05:29.501: E/AndroidRuntime(802): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
07-02 05:05:29.501: E/AndroidRuntime(802): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
07-02 05:05:29.501: E/AndroidRuntime(802): at android.app.ActivityThread.access$600(ActivityThread.java:141)
07-02 05:05:29.501: E/AndroidRuntime(802): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
07-02 05:05:29.501: E/AndroidRuntime(802): at android.os.Handler.dispatchMessage(Handler.java:99)
07-02 05:05:29.501: E/AndroidRuntime(802): at android.os.Looper.loop(Looper.java:137)
07-02 05:05:29.501: E/AndroidRuntime(802): at android.app.ActivityThread.main(ActivityThread.java:5041)
07-02 05:05:29.501: E/AndroidRuntime(802): at java.lang.reflect.Method.invokeNative(Native Method)
07-02 05:05:29.501: E/AndroidRuntime(802): at java.lang.reflect.Method.invoke(Method.java:511)
07-02 05:05:29.501: E/AndroidRuntime(802): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
07-02 05:05:29.501: E/AndroidRuntime(802): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
07-02 05:05:29.501: E/AndroidRuntime(802): at dalvik.system.NativeStart.main(Native Method)
07-02 05:05:29.501: E/AndroidRuntime(802): Caused by: java.lang.NullPointerException
07-02 05:05:29.501: E/AndroidRuntime(802): at java.lang.StringToReal.parseDouble(StringToReal.java:244)
07-02 05:05:29.501: E/AndroidRuntime(802): at java.lang.Double.parseDouble(Double.java:295)
07-02 05:05:29.501: E/AndroidRuntime(802): at com.example.sample.CartActivity.onCreate(CartActivity.java:54)
07-02 05:05:29.501: E/AndroidRuntime(802): at android.app.Activity.performCreate(Activity.java:5104)
07-02 05:05:29.501: E/AndroidRuntime(802): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
07-02 05:05:29.501: E/AndroidRuntime(802): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
07-02 05:05:29.501: E/AndroidRuntime(802): ... 11 more
07-02 05:05:33.180: I/Process(802): Sending signal. PID: 802 SIG: 9
(1)有一種方法將值從適配器傳遞到設置了適配器的活動,
即我們編寫listview.setadapter(xyzadapter); 在MainActivity中,我們希望將值從xyzadapter傳遞給MainActivity,然后我只知道一種方法,建立一個接口,在其中定義一個方法以傳遞值的參數,然后在適配器類上實現它,
(2)如果要將值從適配器傳遞到另一個未設置它的活動,則可以使用putExtra方法傳遞值,
讓我知道您是否有任何問題...
編輯:針對(1)個答案
在主程序包中創建一個接口:
public interface DataTransferInterface {
public void setValues(ArrayList<?> al);
}
在您的適配器類中,將接口作為對象:
在此行下的公共類CartAdapter擴展BaseAdapter {並在構造方法之前:
DataTransferInterface dtInterface;
在您的建築中通過此界面
在CartAdapter中使用以下構造函數:
public CartAdapter(Activity a, DataTransferInterface dtInterface) {
// TODO Auto-generated constructor stub
activity = a;
this.dtInterface = dtInterface;
inflater = (LayoutInflater) activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
並使用dtInterface.setValues(您的值傳遞給Activity)
現在在您的CartActivity.java中
實現該接口,例如:
public class CartActivity extends Activity implements DataTransferInterface {
並改變
mViewCartAdpt = new CartAdapter(CartActivity.this);
至
mViewCartAdpt = new CartAdapter(CartActivity.this, this);
現在,您將在CartActivity(在CartActivity上移動鼠標光標)下方看到紅線,其中顯示添加未實現的方法,單擊該行將覆蓋setValues方法
@Override
public void setValues(ArrayList<?> al) {
// TODO Auto-generated method stub
}
您可以使用任何類型的數據而不是ArrayList進行傳遞
讓我知道您是否有什么用處:
使用共享的首選項從適配器到活動獲取數據
該行代碼的問題在於,您有許多調用在其中一個函數返回null的地方安靜下來。 您應該像這樣將其拆分:
SomeType1 detail = Constants.sItem_Detail;
SomeType2 something = detail.get(i);
String strValue = something.get(com.example.sample.CartAdapter.KEY_TOTAL);
mGTotal += Double.parseDouble(strValue);
因此,您會更快地發現問題。 順便說一句,您還應該在每一行中檢查該值是否為null。
還請注意, longVar = longVar + longValue
可以簡化為longVar += longValue
。
還有另一種方法。
您可以在構造函數中傳遞viewID
或view object
,並從適配器設置更新后的值。
它將100%工作。 它為我工作。
它們是我使用的一種方法,我在Class中定義了一個靜態數組,然后從適配器類訪問該數組。 因此,只要它們是適配器中的值更改,我的列表值就會反映在類本身中。
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