android权限

android在6.0版本之前只需要在AndroidManifest.xml文件中添加权限就够了。在6.0之后就需要对部分权限即危险权限进行运行时权限申请，不然就会系统报错。
我们以打电话为示例

public class PermissionActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_permission);
        Button permission = (Button) findViewById(R.id.permission);
        permission.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                call();
            }
        });
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        switch (requestCode) {
            case 1:
                if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {//3.申请权限的回调方法，当权限申请成功时再拨打电话。
                    call();
                } else {
                    Toast.makeText(PermissionActivity.this, "您拒绝了拨打电话的权限申请", Toast.LENGTH_SHORT).show();//如果拒绝了，则提示用户被拒绝
                }
                break;
        }
    }

    /**
     * 拨打电话需要先申请权限，
     */
    private void call() {
        if (ActivityCompat.checkSelfPermission(PermissionActivity.this, Manifest.permission.CALL_PHONE) != PackageManager.PERMISSION_GRANTED) {//1.先判断是否已经申请了打电话的权限
            //    ActivityCompat#requestPermissions
            // here to request the missing permissions, and then overriding
            //   public void onRequestPermissionsResult(int requestCode, String[] permissions,
            //                                          int[] grantResults)
            // to handle the case where the user grants the permission. See the documentation
            // for ActivityCompat#requestPermissions for more details.
            ActivityCompat.requestPermissions(PermissionActivity.this, new String[]{Manifest.permission.CALL_PHONE}, 1);//2.如果没有则继续申请打电话权限
        } else {
            Intent intent = new Intent(Intent.ACTION_CALL);
            intent.setData(Uri.parse("tel:10086"));
            startActivity(intent);//如果已经申请了权限则直接拨打电话
        }
    }