我在android编程时遇到问题,我有一个需要运行一些例程(例如扫描某些条形码)的应用.
扫描完条形码后,我会将条形码的数据发送到我的API,“等待”以获取一些信息,然后做其他事情.
问题是当我调用我的API来获取信息,并尝试使用应该来自API的信息后,我陷入了NULL异常,请参见以下代码：
每次扫描条形码时都会调用的扫描例程：
// 1 - First Stage: Scan barcode of tank
if(stageScannerTank == 1)
{
// Verify if the user scanned the correct Tank
if (!resultScan.equals(expectedTank)) {
Toast.makeText(getContext(), "Wrong Tank, scan the correct ", Toast.LENGTH_LONG).show();
stageScannerTank = 0;
return;
}
// Get the tank information
//new TanqueTask().execute(resultScan);
**HERE IS MY PROBLEM, When I call the function below, I fill my tankMixPlant with data**
getTankMixPlant(resultScan);
** I always fall into this IF **
// If null information
if(tankMixPlant == null) {
Toast.makeText(getContext(), "Error to read tank information", Toast.LENGTH_LONG).show();
return;
}
}
getTankMixPlant,使用Retrofit来调用我的服务,如果我超出常规测试,它就可以正常工作：
private void getTankMixPlant(String tankName){
mService.getTankMixPlant(tankName).enqueue(new Callback<TankMixPlant>() {
@Override
public void onResponse(Call<TankMixPlant> call, Response<TankMixPlant> response) {
tankMixPlant = response.body();
}
@Override
public void onFailure(Call<TankMixPlant> call, Throwable t) {
// On failure show the error message to the User
AlertDialog alert;
AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
builder.setTitle("Error");
builder.setMessage("Error: " + t.getMessage());
alert = builder.create();
alert.show();
}
});
}
如何等待tankMixPlant充满数据以继续执行我的例程？
更新：
我继续解决该问题,但是我更改了一些可以在下面看到的内容：
现在我得到了NullPointerException.
现在,我验证onResponse方法内的对象是否为null：
private void getTankMixPlant(String tankName){
mService.getTankMixPlant(tankName).enqueue(new Callback<TankMixPlant>() {
@Override
public void onResponse(Call<TankMixPlant> call, Response<TankMixPlant> response) {
tankMixPlant = response.body();
if(tankMixPlant == null) {
Toast.makeText(getContext(), "Error to read tank information",
Toast.LENGTH_LONG).show();
return;
}
}
@Override
public void onFailure(Call<TankMixPlant> call, Throwable t) {
// On failure show the error message to the User
AlertDialog alert;
AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
builder.setTitle("Error");
builder.setMessage("Error: " + t.getMessage());
alert = builder.create();
alert.show();
}
});
}
但是,当我尝试验证有关tankMixPlant的一些信息时：
// Verify tank stage
if(!tankMixPlant.getBlenderCode().equals("0") && tankMixPlant.getIngr() == 1)
{
getPackages(tankMixPlant.getRecipeNumber(), tankMixPlant.getBlenderCode(), tankMixPlant.getTankName());
// 2 - Mix Packages: Scan package barcode
stageScannerTank = 2;
}
if(!tankMixPlant.getIngrSAPNumber().equals("0") && tankMixPlant.getIngr() == 1)
{
getIngr(tankMixPlant.getRecipeNumber(), tankMixPlant.getTankName());
// 3 - P.I Packages: Scan package barcode
stageScannerTank = 3;
}
我的应用因以下错误而崩溃：
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.labtse.kibonapp, PID: 21519
java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=114910, result=-1, data=Intent { act=com.google.zxing.client.android.SCAN flg=0x80000 VirtualScreenParam=Params{mDisplayId=-1, null, mFlags=0x00000000)} (has extras) }} to activity {com.example.labtse.kibonapp/com.example.labtse.kibonapp.TabPagesActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.example.labtse.kibonapp.model.TankMixPlant.getBlenderCode()' on a null object reference
at android.app.ActivityThread.deliverResults(ActivityThread.java:5007)
at android.app.ActivityThread.handleSendResult(ActivityThread.java:5050)
at android.app.ActivityThread.access$1600(ActivityThread.java:230)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1876)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:7409)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.example.labtse.kibonapp.model.TankMixPlant.getBlenderCode()' on a null object reference
at com.example.labtse.kibonapp.MixPlantFragment.scanRoutine(MixPlantFragment.java:367)
at com.example.labtse.kibonapp.MixPlantFragment.onActivityResult(MixPlantFragment.java:399)
at android.support.v4.app.FragmentActivity.onActivityResult(FragmentActivity.java:151)
at android.app.Activity.dispatchActivityResult(Activity.java:7165)
at android.app.ActivityThread.deliverResults(ActivityThread.java:5003)
at android.app.ActivityThread.handleSendResult(ActivityThread.java:5050)
at android.app.ActivityThread.access$1600(ActivityThread.java:230)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1876)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:7409)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)
我的tankMixPlant类：
package com.example.labtse.kibonapp.model;
public class TankMixPlant {
private String tankName;
private String recipeNumber;
private int idBatch;
private String ingrSAPNumber;
private String blenderCode;
private short ingr;
private boolean QRUN;
private boolean QEND;
private Boolean QDOSANDO;
private Boolean CONF_ING;
public TankMixPlant() {
}
public String getTankName() {
return tankName;
}
public void setTankName(String tankName) {
this.tankName = tankName;
}
public String getRecipeNumber() {
return recipeNumber;
}
public void setRecipeNumber(String recipeNumber) {
this.recipeNumber = recipeNumber;
}
public int getIdBatch() {
return idBatch;
}
public void setIdBatch(int idBatch) {
this.idBatch = idBatch;
}
public String getIngrSAPNumber() {
return ingrSAPNumber;
}
public void setIngrSAPNumber(String ingrSAPNumber) {
this.ingrSAPNumber = ingrSAPNumber;
}
public String getBlenderCode() {
return blenderCode;
}
public void setBlenderCode(String blenderCode) {
this.blenderCode = blenderCode;
}
public short getIngr() {
return ingr;
}
public void setIngr(short ingr) {
this.ingr = ingr;
}
public boolean isQRUN() {
return QRUN;
}
public void setQRUN(boolean QRUN) {
this.QRUN = QRUN;
}
public boolean isQEND() {
return QEND;
}
public void setQEND(boolean QEND) {
this.QEND = QEND;
}
public Boolean getQDOSANDO() {
return QDOSANDO;
}
public void setQDOSANDO(Boolean QDOSANDO) {
this.QDOSANDO = QDOSANDO;
}
public Boolean getCONF_ING() {
return CONF_ING;
}
public void setCONF_ING(Boolean CONF_ING) {
this.CONF_ING = CONF_ING;
}
}
解决方法:
解：
您必须这样写：
if(tankMixPlant == null) {
Toast.makeText(getContext(), "Error to read tank information", Toast.LENGTH_LONG).show();
return;
}
在您的onResponse内部,行tankplant = …之后
现在,如果您从服务器获取任何数据,则将消除空异常.
希望能帮助到你.
更新1：
这样写：
if(!tankMixPlant.getBlenderCode().equals("0") && tankMixPlant.getIngr() == 1)
{
getPackages(tankMixPlant.getRecipeNumber(), tankMixPlant.getBlenderCode(), tankMixPlant.getTankName());
// 2 - Mix Packages: Scan package barcode
stageScannerTank = 2;
}
if(!tankMixPlant.getIngrSAPNumber().equals("0") && tankMixPlant.getIngr() == 1)
{
getIngr(tankMixPlant.getRecipeNumber(), tankMixPlant.getTankName());
// 3 - P.I Packages: Scan package barcode
stageScannerTank = 3;
}
在您的onResponse方法中,如下所示：
private void getTankMixPlant(String tankName){
mService.getTankMixPlant(tankName).enqueue(new Callback<TankMixPlant>() {
@Override
public void onResponse(Call<TankMixPlant> call, Response<TankMixPlant> response) {
tankMixPlant = response.body();
if(tankMixPlant == null) {
Toast.makeText(getContext(), "Error to read tank information",
Toast.LENGTH_LONG).show();
return;
}
...... (Write Here)
}
@Override
public void onFailure(Call<TankMixPlant> call, Throwable t) {
// On failure show the error message to the User
AlertDialog alert;
AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
builder.setTitle("Error");
builder.setMessage("Error: " + t.getMessage());
alert = builder.create();
alert.show();
}
});
试试吧.