Android：等待API做出响应,然后再使用Retrofit继续执行

概述我在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

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.access00(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.access00(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.

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