Android Gson

转自：http://www.stormzhang.com/android/2014/05/22/android-gson/

Json格式化校验工具：kjson

Gson的官方下载地址：google-gson

导入Gson包

复制gson-2.4.jar到UseGson\app\libs

AndroidStudio右键gson-2.4.jar -> add as library

会自动在app/build.gradle里

dependencies {
compile fileTree(include: ['*.jar'], dir: 'libs')
compile 'com.android.support:appcompat-v7:22.1.1'
compile files('libs/gson-2.4.jar')
}

单个对象

假设Json的数据格式是这样：

{
"id": 100,
"body": "It is my post",
"number": 0.13,
"created_at": "2014-05-22 19:12:38"
}

定义对应的类

public class Foo {
public int id;
public String body;
public float number;
public String created_at;
}

created_at不是java风格，java编程规范是驼峰结构，Gson很人性化的也提供注解的方式，只需要把Foo对象改成:

public class Foo {
public int id;
public String body;
public float number;

@SerializedName("created_at")
public String createdAt;
}

使用Gson

public static final String JSON_DATA = "...";
Foo foo = new Gson().fromJson(JSON_DATA, Foo.class);

这里created_at直接定义了String类型，如果想要Data类型也可以：

public class Foo {
public int id;
public String body;
public float number;
public Date created_at;
}

public static final String JSON_DATA = "...";
GsonBuilder gsonBuilder = new GsonBuilder();
gsonBuilder.setDateFormat("yyyy-MM-dd HH:mm:ss");
Gson gson = gsonBuilder.create();
Foo foo = gson.fromJson(JSON_DATA, Foo.class);

对象的嵌套

假设Json的数据格式是这样：

{
"id": 100,
"body": "It is my post",
"number": 0.13,
"created_at": "2014-05-22 19:12:38",
"foo2": {
"id": 200,
"name": "haha"
}
}

那么定义的对象是这样：

public class Foo {
public int id;
public String body;
public float number;
public String created_at;
public ChildFoo foo2;

public class ChildFoo {
public int id;
public String name;
}
}

对象数组

json数组：

[{
"id": 100,
"body": "It is my post1",
"number": 0.13,
"created_at": "2014-05-20 19:12:38"
},
{
"id": 101,
"body": "It is my post2",
"number": 0.14,
"created_at": "2014-05-22 19:12:38"
}]

这种解析有两种方法:

1. 解析成数组

public static final String JSON_DATA = "...";
Foo[] foos = new Gson().fromJson(JSON_DATA, Foo[].class);
// 这时候想转成List的话调用如下方法
// List<Foo> foosList = Arrays.asList(foos);

2. 解析成List

public static final String JSON_DATA = "...";
Type listType = new TypeToken<ArrayList<Foo>>(){}.getType();
ArrayList<Foo> foos = new Gson().fromJson(JSON_DATA, listType);

1. 添加Gson包

复制gson-2.4.jar到UseGson\app\libs

AndroidStudio右键gson-2.4.jar -> add as library

2. app\src\main\assets

singleObject (new时选择Json格式)

{
"id": 100,
"body": "It is my post",
"number": 0.13,
"created_at": "2015-10-09 14:12:30"
}

nestedObject (new时选择Json格式)

{
"id": 100,
"body": "It is my post",
"number": 0.13,
"created_at": "2014-05-22 19:12:38",
"child": {
"id": 200,
"name": "haha"
}
}

arrayObject (new时选择Json格式)

[{
"id": 100,
"body": "It is my post1",
"number": 0.13,
"created_at": "2014-05-20 19:12:38"
},
{
"id": 101,
"body": "It is my post2",
"number": 0.14,
"created_at": "2014-05-22 19:12:38"
}]

3. 对应的类

SingleObject.java

package com.silion.usegson;

import com.google.gson.annotations.SerializedName;

/**
* Created by silion on 2015/10/9.
*/
public class SingleObject {
public int id;
public String body;
public float number;
//public String created_at;
@SerializedName("created_at")
public String createdAt;

public String toString() {
return "SingleObject id = " + id + ", body = " + body +
", number = " + number + ", createdAt = " + createdAt;
}
}

SingleObjectData.java

package com.silion.usegson;

import java.util.Date;

/**
* Created by silion on 2015/10/9.
*/
public class SingleObjectData {
public int id;
public String body;
public float number;
public Date created_at;

public String toString() {
return "SingleObjectData id = " + id + ", body = " + body +
", number = " + number + ", created_at = " + created_at;
}
}

NestedObject.java

package com.silion.usegson;

/**
* Created by silion on 2015/10/9.
*/
public class NestedObject {
public int id;
public String body;
public float number;
public String created_at;
public Child child;

public class Child {
public int id;
public String name;
}

public String toString() {
return "NestedObject id = " + id + ", body = " + body +
", number = " + number + ", createdAt = " + created_at +
"\n" +"child = " + this.child.id + ", " + this.child.name;
}
}

4. 布局

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:orientation="vertical"
tools:context=".MainActivity">

<Button
android:id="@+id/single"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="@string/single" />

<Button
android:id="@+id/nested"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="@string/nested" />

<Button
android:id="@+id/array"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="@string/array" />
</LinearLayout>

5. MainActivity.java

package com.silion.usegson;

import android.app.Activity;
import android.content.res.AssetManager;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.reflect.TypeToken;

import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.lang.reflect.Type;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class MainActivity extends Activity {

View.OnClickListener mClickListener = new View.OnClickListener() {
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.single: {
AssetManager assetManager = MainActivity.this.getAssets();
try {
SingleObject object = new Gson().fromJson(new InputStreamReader(assetManager.open("singleObject")), SingleObject.class);
android.util.Log.v("slong.liang", object.toString());

GsonBuilder gsonBuilder = new GsonBuilder();
gsonBuilder.setDateFormat("yyyy-mm-dd HH:mm:ss");
SingleObjectData objectData = gsonBuilder.create().fromJson(new InputStreamReader(assetManager.open("singleObject")), SingleObjectData.class);
android.util.Log.v("slong.liang", objectData.toString());
} catch (IOException e) {
e.printStackTrace();
}
break;
}
case R.id.nested: {
AssetManager assetManager = MainActivity.this.getAssets();
Reader json = null;
try {
InputStream is = assetManager.open("nestedObject");
json = new InputStreamReader(is);
} catch (IOException e) {
e.printStackTrace();
}
NestedObject object = new Gson().fromJson(json, NestedObject.class);
android.util.Log.v("slong.liang", object.toString());
break;
}
case R.id.array: {
AssetManager assetManager = MainActivity.this.getAssets();

Reader json1 = null;
try {
json1 = new InputStreamReader(assetManager.open("arrayObject"));
} catch (IOException e) {
e.printStackTrace();
}

//解析成数组
Gson gson = new Gson();
SingleObject[] objects = gson.fromJson(json1, SingleObject[].class);
List<SingleObject> objectList1 = Arrays.asList(objects);
android.util.Log.v("slong.liang", "-------Array method 1--------");
for(SingleObject object : objectList1)
b355
{
android.util.Log.v("slong.liang", object.toString());
}

Reader json2 = null;
try {
json2 = new InputStreamReader(assetManager.open("arrayObject"));
} catch (IOException e) {
e.printStackTrace();
}

//解析成List
Type listType = new TypeToken<ArrayList<SingleObject>>(){}.getType();
List<SingleObject> objectList2 = gson.fromJson(json2, listType);
android.util.Log.v("slong.liang", "-------Array method 2--------");
for(SingleObject object : objectList2) {
android.util.Log.v("slong.liang", object.toString());
}
break;
}
default:
break;
}
}
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button singleButton = (Button) findViewById(R.id.single);
singleButton.setOnClickListener(mClickListener);
Button nestedButton = (Button) findViewById(R.id.nested);
nestedButton.setOnClickListener(mClickListener);
Button arrayButton = (Button) findViewById(R.id.array);
arrayButton.setOnClickListener(mClickListener);
}
}