Question

我已经为全局变量创建了其他类，现在我只想这样抛出它：

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity1);
    class2 global;

    global = (class2)getApplicationContext();

我收到错误：

android.app.Application无法强制转换为eu.tools.test_training_home.class2

class2：

public class class2 extends Application {

    private String name="name1";
    private int number =0;

Answer 1

此处getApplicationContext()返回类Context的对象，但不返回class2。

检查https://stackoverflow.com/a/907368/1435132。

请参阅Custom global Application class breaks with "android.app.Application cannot be cast to"

Answer 2

问题是Class2中的Consructor 进入class2，我有1个constuctor，2个setter，2个getter 我删除了构造函数，然后错误没来了

public class class2 extends Application {

private String name ="name1";
private int number =10;

public class2(String name, int number) { // this was the problem
    this.name = name;
    this.number = number;
}

public void setName(String name) {
    this.name = name;
}

public void setNumber(int number) {
    this.number = number;
}

public String getName() {
    return name;
}

public int getNumber() {
    return number;
}

}

通过强制转换类出错

2 个答案: